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	$110.98	3.201%	$114.5325	$114.53	$114.55	$114.50
Purchase #2	$48.37	7.646%	$52.0684	$52.07	$52.05	$52.10
Purchase #3	$246.65	13.280%	$279.4051	$279.41	$279.40	$279.40
Purchase #4	$55.78	6.377%	$59.3371	$59.34	$59.35	$59.30
Purchase #5	$160.52	8.615%	$174.3488	$174.35	$174.35	$174.30
Purchase #6	$172.47	8.308%	$186.7988	$186.80	$186.80	$186.80
Purchase #7	$24.95	13.748%	$28.3801	$28.38	$28.40	$28.40
7 purchase totals =	$819.72		$894.8708	$894.88	$894.90	$894.80