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	$127.98	7.472%	$137.5427	$137.54	$137.55	$137.50
Purchase #2	$152.61	6.526%	$162.5693	$162.57	$162.55	$162.60
Purchase #3	$105.45	7.269%	$113.1152	$113.12	$113.10	$113.10
Purchase #4	$49.67	13.676%	$56.4629	$56.46	$56.45	$56.50
Purchase #5	$127.33	6.523%	$135.6357	$135.64	$135.65	$135.60
Purchase #6	$163.95	10.777%	$181.6189	$181.62	$181.60	$181.60
Purchase #7	$189.72	13.432%	$215.2032	$215.20	$215.20	$215.20
7 purchase totals =	$916.71		$1,002.1479	$1,002.15	$1,002.10	$1,002.10