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	$117.69	5.704%	$124.403	$124.40	$124.40	$124.40
Purchase #2	$5.59	13.188%	$6.3272	$6.33	$6.35	$6.30
Purchase #3	$73.46	7.700%	$79.1164	$79.12	$79.10	$79.10
Purchase #4	$34.84	10.310%	$38.432	$38.43	$38.45	$38.40
Purchase #5	$25.81	11.145%	$28.6865	$28.69	$28.70	$28.70
Purchase #6	$72.88	8.139%	$78.8117	$78.81	$78.80	$78.80
Purchase #7	$172.36	4.225%	$179.6422	$179.64	$179.65	$179.60
7 purchase totals =	$502.63		$535.4190	$535.42	$535.45	$535.30