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	$160.38	3.665%	$166.2579	$166.26	$166.25	$166.30
Purchase #2	$161.81	8.188%	$175.059	$175.06	$175.05	$175.10
Purchase #3	$94.61	6.537%	$100.7947	$100.79	$100.80	$100.80
Purchase #4	$240.58	6.648%	$256.5738	$256.57	$256.55	$256.60
Purchase #5	$45.54	10.486%	$50.3153	$50.32	$50.30	$50.30
Purchase #6	$250.82	6.145%	$266.2329	$266.23	$266.25	$266.20
Purchase #7	$44.93	5.165%	$47.2506	$47.25	$47.25	$47.30
7 purchase totals =	$998.67		$1,062.4842	$1,062.48	$1,062.45	$1,062.60