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	$223.29	4.694%	$233.7712	$233.77	$233.75	$233.80
Purchase #2	$144.71	6.728%	$154.4461	$154.45	$154.45	$154.40
Purchase #3	$31.80	4.498%	$33.2304	$33.23	$33.25	$33.20
Purchase #4	$65.88	10.174%	$72.5826	$72.58	$72.60	$72.60
Purchase #5	$148.61	7.163%	$159.2549	$159.25	$159.25	$159.30
Purchase #6	$56.62	5.265%	$59.601	$59.60	$59.60	$59.60
Purchase #7	$140.93	3.792%	$146.2741	$146.27	$146.25	$146.30
7 purchase totals =	$811.84		$859.1603	$859.15	$859.15	$859.20