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	$51.25	3.766%	$53.1801	$53.18	$53.20	$53.20
Purchase #2	$73.37	7.248%	$78.6879	$78.69	$78.70	$78.70
Purchase #3	$78.54	3.674%	$81.4256	$81.43	$81.45	$81.40
Purchase #4	$95.31	12.412%	$107.1399	$107.14	$107.15	$107.10
Purchase #5	$221.80	12.307%	$249.0969	$249.10	$249.10	$249.10
Purchase #6	$225.35	11.306%	$250.8281	$250.83	$250.85	$250.80
Purchase #7	$141.77	4.560%	$148.2347	$148.23	$148.25	$148.20
7 purchase totals =	$887.39		$968.5932	$968.60	$968.70	$968.50