Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$173.55	10.691%	$192.1042	$192.10	$192.10	$192.10
Purchase #2	$96.43	7.602%	$103.7606	$103.76	$103.75	$103.80
Purchase #3	$237.82	11.143%	$264.3203	$264.32	$264.30	$264.30
Purchase #4	$133.50	10.400%	$147.384	$147.38	$147.40	$147.40
Purchase #5	$200.88	4.313%	$209.544	$209.54	$209.55	$209.50
Purchase #6	$137.92	9.573%	$151.1231	$151.12	$151.10	$151.10
Purchase #7	$104.63	12.656%	$117.872	$117.87	$117.85	$117.90
7 purchase totals =	$1,084.73		$1,186.1082	$1,186.09	$1,186.05	$1,186.10