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	$60.56	11.813%	$67.714	$67.71	$67.70	$67.70
Purchase #2	$115.76	6.839%	$123.6768	$123.68	$123.70	$123.70
Purchase #3	$194.59	6.136%	$206.53	$206.53	$206.55	$206.50
Purchase #4	$79.87	4.680%	$83.6079	$83.61	$83.60	$83.60
Purchase #5	$143.96	12.345%	$161.7319	$161.73	$161.75	$161.70
Purchase #6	$106.98	5.788%	$113.172	$113.17	$113.15	$113.20
Purchase #7	$36.59	5.814%	$38.7173	$38.72	$38.70	$38.70
7 purchase totals =	$738.31		$795.1499	$795.15	$795.15	$795.10