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	$61.48	9.627%	$67.3987	$67.40	$67.40	$67.40
Purchase #2	$247.44	6.739%	$264.115	$264.12	$264.10	$264.10
Purchase #3	$185.67	10.439%	$205.0521	$205.05	$205.05	$205.10
Purchase #4	$60.27	3.406%	$62.3228	$62.32	$62.30	$62.30
Purchase #5	$121.60	4.868%	$127.5195	$127.52	$127.50	$127.50
Purchase #6	$169.82	4.472%	$177.4144	$177.41	$177.40	$177.40
Purchase #7	$90.56	6.468%	$96.4174	$96.42	$96.40	$96.40
7 purchase totals =	$936.84		$1,000.2399	$1,000.24	$1,000.15	$1,000.20