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	$49.89	7.652%	$53.7076	$53.71	$53.70	$53.70
Purchase #2	$89.53	7.455%	$96.2045	$96.20	$96.20	$96.20
Purchase #3	$244.29	5.740%	$258.3122	$258.31	$258.30	$258.30
Purchase #4	$239.54	13.740%	$272.4528	$272.45	$272.45	$272.50
Purchase #5	$43.46	12.164%	$48.7465	$48.75	$48.75	$48.70
Purchase #6	$109.74	12.349%	$123.2918	$123.29	$123.30	$123.30
Purchase #7	$234.88	4.227%	$244.8084	$244.81	$244.80	$244.80
7 purchase totals =	$1,011.33		$1,097.5238	$1,097.52	$1,097.50	$1,097.50