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	$167.53	9.489%	$183.4269	$183.43	$183.45	$183.40
Purchase #2	$250.70	8.668%	$272.4307	$272.43	$272.45	$272.40
Purchase #3	$72.95	12.854%	$82.327	$82.33	$82.35	$82.30
Purchase #4	$64.29	10.692%	$71.1639	$71.16	$71.15	$71.20
Purchase #5	$126.41	11.606%	$141.0811	$141.08	$141.10	$141.10
Purchase #6	$104.59	7.440%	$112.3715	$112.37	$112.35	$112.40
Purchase #7	$147.40	3.772%	$152.9599	$152.96	$152.95	$153.00
7 purchase totals =	$933.87		$1,015.7610	$1,015.76	$1,015.80	$1,015.80