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	$148.82	12.309%	$167.1383	$167.14	$167.15	$167.10
Purchase #2	$40.65	11.700%	$45.4061	$45.41	$45.40	$45.40
Purchase #3	$194.51	3.383%	$201.0903	$201.09	$201.10	$201.10
Purchase #4	$106.56	9.398%	$116.5745	$116.57	$116.55	$116.60
Purchase #5	$82.27	4.708%	$86.1433	$86.14	$86.15	$86.10
Purchase #6	$96.88	3.688%	$100.4529	$100.45	$100.45	$100.50
Purchase #7	$234.97	12.676%	$264.7548	$264.75	$264.75	$264.80
7 purchase totals =	$904.66		$981.5602	$981.55	$981.55	$981.60