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	$164.71	13.485%	$186.9211	$186.92	$186.90	$186.90
Purchase #2	$167.49	8.786%	$182.2057	$182.21	$182.20	$182.20
Purchase #3	$11.31	5.604%	$11.9438	$11.94	$11.95	$11.90
Purchase #4	$77.27	10.118%	$85.0882	$85.09	$85.10	$85.10
Purchase #5	$243.94	10.265%	$268.9804	$268.98	$269.00	$269.00
Purchase #6	$78.66	4.405%	$82.125	$82.13	$82.15	$82.10
Purchase #7	$115.50	10.500%	$127.6275	$127.63	$127.65	$127.60
7 purchase totals =	$858.88		$944.8917	$944.90	$944.95	$944.80