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	$65.39	11.278%	$72.7647	$72.76	$72.75	$72.80
Purchase #2	$55.52	11.694%	$62.0125	$62.01	$62.00	$62.00
Purchase #3	$51.33	3.219%	$52.9823	$52.98	$53.00	$53.00
Purchase #4	$124.42	11.368%	$138.5641	$138.56	$138.55	$138.60
Purchase #5	$81.25	12.505%	$91.4103	$91.41	$91.40	$91.40
Purchase #6	$156.61	3.168%	$161.5714	$161.57	$161.55	$161.60
Purchase #7	$211.74	5.509%	$223.4048	$223.40	$223.40	$223.40
7 purchase totals =	$746.26		$802.7101	$802.69	$802.65	$802.80