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	$33.65	8.318%	$36.449	$36.45	$36.45	$36.40
Purchase #2	$89.87	8.378%	$97.3993	$97.40	$97.40	$97.40
Purchase #3	$84.40	6.326%	$89.7391	$89.74	$89.75	$89.70
Purchase #4	$23.52	6.846%	$25.1302	$25.13	$25.15	$25.10
Purchase #5	$73.76	6.480%	$78.5396	$78.54	$78.55	$78.50
Purchase #6	$53.67	13.184%	$60.7459	$60.75	$60.75	$60.70
Purchase #7	$91.74	8.867%	$99.8746	$99.87	$99.85	$99.90
7 purchase totals =	$450.61		$487.8777	$487.88	$487.90	$487.70