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	$90.82	5.819%	$96.1048	$96.10	$96.10	$96.10
Purchase #2	$159.52	4.775%	$167.1371	$167.14	$167.15	$167.10
Purchase #3	$48.98	11.778%	$54.7489	$54.75	$54.75	$54.70
Purchase #4	$6.87	5.292%	$7.2336	$7.23	$7.25	$7.20
Purchase #5	$102.90	6.802%	$109.8993	$109.90	$109.90	$109.90
Purchase #6	$78.34	13.226%	$88.7012	$88.70	$88.70	$88.70
Purchase #7	$95.46	3.219%	$98.5329	$98.53	$98.55	$98.50
7 purchase totals =	$582.89		$622.3578	$622.35	$622.40	$622.20