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	$75.58	13.670%	$85.9118	$85.91	$85.90	$85.90
Purchase #2	$186.54	3.530%	$193.1249	$193.12	$193.10	$193.10
Purchase #3	$145.34	6.729%	$155.1199	$155.12	$155.10	$155.10
Purchase #4	$197.55	12.541%	$222.3247	$222.32	$222.30	$222.30
Purchase #5	$99.72	11.609%	$111.2965	$111.30	$111.30	$111.30
Purchase #6	$185.65	13.515%	$210.7406	$210.74	$210.75	$210.70
Purchase #7	$76.32	12.655%	$85.9783	$85.98	$86.00	$86.00
7 purchase totals =	$966.70		$1,064.4967	$1,064.49	$1,064.45	$1,064.40