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	$167.45	12.637%	$188.6107	$188.61	$188.60	$188.60
Purchase #2	$151.54	11.759%	$169.3596	$169.36	$169.35	$169.40
Purchase #3	$78.28	9.820%	$85.9671	$85.97	$85.95	$86.00
Purchase #4	$155.90	6.382%	$165.8495	$165.85	$165.85	$165.80
Purchase #5	$118.46	4.269%	$123.5171	$123.52	$123.50	$123.50
Purchase #6	$224.64	13.275%	$254.461	$254.46	$254.45	$254.50
Purchase #7	$41.83	13.800%	$47.6025	$47.60	$47.60	$47.60
7 purchase totals =	$938.10		$1,035.3675	$1,035.37	$1,035.30	$1,035.40