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	$88.79	8.267%	$96.1303	$96.13	$96.15	$96.10
Purchase #2	$148.75	5.374%	$156.7438	$156.74	$156.75	$156.70
Purchase #3	$40.25	4.649%	$42.1212	$42.12	$42.10	$42.10
Purchase #4	$169.46	6.501%	$180.4766	$180.48	$180.50	$180.50
Purchase #5	$27.49	10.644%	$30.416	$30.42	$30.40	$30.40
Purchase #6	$63.89	9.668%	$70.0669	$70.07	$70.05	$70.10
Purchase #7	$88.69	13.613%	$100.7634	$100.76	$100.75	$100.80
7 purchase totals =	$627.32		$676.7182	$676.72	$676.70	$676.70