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	$118.61	7.170%	$127.1143	$127.11	$127.10	$127.10
Purchase #2	$28.62	13.145%	$32.3821	$32.38	$32.40	$32.40
Purchase #3	$104.76	8.349%	$113.5064	$113.51	$113.50	$113.50
Purchase #4	$187.46	13.598%	$212.9508	$212.95	$212.95	$213.00
Purchase #5	$124.97	4.161%	$130.17	$130.17	$130.15	$130.20
Purchase #6	$207.59	12.395%	$233.3208	$233.32	$233.30	$233.30
Purchase #7	$206.85	13.584%	$234.9485	$234.95	$234.95	$234.90
7 purchase totals =	$978.86		$1,084.3929	$1,084.39	$1,084.35	$1,084.40