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	$68.90	8.586%	$74.8158	$74.82	$74.80	$74.80
Purchase #2	$146.40	4.323%	$152.7289	$152.73	$152.75	$152.70
Purchase #3	$124.61	3.374%	$128.8143	$128.81	$128.80	$128.80
Purchase #4	$168.65	12.336%	$189.4547	$189.45	$189.45	$189.50
Purchase #5	$175.95	5.511%	$185.6466	$185.65	$185.65	$185.60
Purchase #6	$131.98	4.262%	$137.605	$137.61	$137.60	$137.60
Purchase #7	$54.68	4.700%	$57.25	$57.25	$57.25	$57.30
7 purchase totals =	$871.17		$926.3153	$926.32	$926.30	$926.30