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	$142.93	10.774%	$158.3293	$158.33	$158.35	$158.30
Purchase #2	$46.64	12.472%	$52.4569	$52.46	$52.45	$52.50
Purchase #3	$55.80	7.467%	$59.9666	$59.97	$59.95	$60.00
Purchase #4	$172.95	13.318%	$195.9835	$195.98	$196.00	$196.00
Purchase #5	$136.53	9.234%	$149.1372	$149.14	$149.15	$149.10
Purchase #6	$188.87	9.565%	$206.9354	$206.94	$206.95	$206.90
Purchase #7	$94.44	5.317%	$99.4614	$99.46	$99.45	$99.50
7 purchase totals =	$838.16		$922.2703	$922.28	$922.30	$922.30