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	$35.32	6.596%	$37.6497	$37.65	$37.65	$37.60
Purchase #2	$50.98	10.341%	$56.2518	$56.25	$56.25	$56.30
Purchase #3	$56.66	4.734%	$59.3423	$59.34	$59.35	$59.30
Purchase #4	$14.28	5.435%	$15.0561	$15.06	$15.05	$15.10
Purchase #5	$76.68	3.489%	$79.3554	$79.36	$79.35	$79.40
Purchase #6	$133.33	6.379%	$141.8351	$141.84	$141.85	$141.80
Purchase #7	$165.46	4.158%	$172.3398	$172.34	$172.35	$172.30
7 purchase totals =	$532.71		$561.8302	$561.84	$561.85	$561.80