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	$159.98	13.402%	$181.4205	$181.42	$181.40	$181.40
Purchase #2	$33.95	9.501%	$37.1756	$37.18	$37.20	$37.20
Purchase #3	$181.55	9.794%	$199.331	$199.33	$199.35	$199.30
Purchase #4	$47.28	3.198%	$48.792	$48.79	$48.80	$48.80
Purchase #5	$83.91	3.283%	$86.6648	$86.66	$86.65	$86.70
Purchase #6	$176.78	11.284%	$196.7279	$196.73	$196.75	$196.70
Purchase #7	$85.47	11.769%	$95.529	$95.53	$95.55	$95.50
7 purchase totals =	$768.92		$845.6408	$845.64	$845.70	$845.60