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	$63.56	4.666%	$66.5257	$66.53	$66.55	$66.50
Purchase #2	$6.48	9.730%	$7.1105	$7.11	$7.10	$7.10
Purchase #3	$136.64	12.664%	$153.9441	$153.94	$153.95	$153.90
Purchase #4	$198.77	3.530%	$205.7866	$205.79	$205.80	$205.80
Purchase #5	$147.78	3.346%	$152.7247	$152.72	$152.70	$152.70
Purchase #6	$216.93	10.137%	$238.9202	$238.92	$238.90	$238.90
Purchase #7	$209.96	11.148%	$233.3663	$233.37	$233.35	$233.40
7 purchase totals =	$980.12		$1,058.3781	$1,058.38	$1,058.35	$1,058.30