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	$226.89	10.743%	$251.2648	$251.26	$251.25	$251.30
Purchase #2	$129.71	12.864%	$146.3959	$146.40	$146.40	$146.40
Purchase #3	$114.78	9.716%	$125.932	$125.93	$125.95	$125.90
Purchase #4	$182.44	12.494%	$205.2341	$205.23	$205.25	$205.20
Purchase #5	$75.42	9.486%	$82.5743	$82.57	$82.55	$82.60
Purchase #6	$182.71	4.112%	$190.223	$190.22	$190.20	$190.20
Purchase #7	$55.26	7.271%	$59.278	$59.28	$59.30	$59.30
7 purchase totals =	$967.21		$1,060.9021	$1,060.89	$1,060.90	$1,060.90