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	$156.94	3.369%	$162.2273	$162.23	$162.25	$162.20
Purchase #2	$105.99	13.559%	$120.3612	$120.36	$120.35	$120.40
Purchase #3	$135.40	12.428%	$152.2275	$152.23	$152.25	$152.20
Purchase #4	$156.72	5.782%	$165.7816	$165.78	$165.80	$165.80
Purchase #5	$241.54	10.677%	$267.3292	$267.33	$267.35	$267.30
Purchase #6	$82.31	12.853%	$92.8893	$92.89	$92.90	$92.90
Purchase #7	$109.74	13.123%	$124.1412	$124.14	$124.15	$124.10
7 purchase totals =	$988.64		$1,084.9573	$1,084.96	$1,085.05	$1,084.90