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	$104.63	5.401%	$110.2811	$110.28	$110.30	$110.30
Purchase #2	$111.85	7.110%	$119.8025	$119.80	$119.80	$119.80
Purchase #3	$47.39	7.459%	$50.9248	$50.92	$50.90	$50.90
Purchase #4	$64.92	10.340%	$71.6327	$71.63	$71.65	$71.60
Purchase #5	$38.59	9.167%	$42.1275	$42.13	$42.15	$42.10
Purchase #6	$31.89	8.233%	$34.5155	$34.52	$34.50	$34.50
Purchase #7	$96.84	9.557%	$106.095	$106.10	$106.10	$106.10
7 purchase totals =	$496.11		$535.3791	$535.38	$535.40	$535.30