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	$105.74	9.615%	$115.9069	$115.91	$115.90	$115.90
Purchase #2	$147.46	7.693%	$158.8041	$158.80	$158.80	$158.80
Purchase #3	$229.52	5.663%	$242.5177	$242.52	$242.50	$242.50
Purchase #4	$48.79	3.138%	$50.321	$50.32	$50.30	$50.30
Purchase #5	$202.77	4.514%	$211.923	$211.92	$211.90	$211.90
Purchase #6	$125.79	9.359%	$137.5627	$137.56	$137.55	$137.60
Purchase #7	$143.40	3.406%	$148.2842	$148.28	$148.30	$148.30
7 purchase totals =	$1,003.47		$1,065.3196	$1,065.31	$1,065.25	$1,065.30