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	$166.85	8.760%	$181.4661	$181.47	$181.45	$181.50
Purchase #2	$187.59	4.811%	$196.615	$196.62	$196.60	$196.60
Purchase #3	$135.85	8.267%	$147.0807	$147.08	$147.10	$147.10
Purchase #4	$91.27	10.409%	$100.7703	$100.77	$100.75	$100.80
Purchase #5	$10.76	3.345%	$11.1199	$11.12	$11.10	$11.10
Purchase #6	$90.80	11.114%	$100.8915	$100.89	$100.90	$100.90
Purchase #7	$6.35	3.368%	$6.5639	$6.56	$6.55	$6.60
7 purchase totals =	$689.47		$744.5074	$744.51	$744.45	$744.60