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	$220.79	13.657%	$250.9433	$250.94	$250.95	$250.90
Purchase #2	$224.59	13.250%	$254.3482	$254.35	$254.35	$254.30
Purchase #3	$96.82	4.250%	$100.9349	$100.93	$100.95	$100.90
Purchase #4	$100.91	8.306%	$109.2916	$109.29	$109.30	$109.30
Purchase #5	$39.73	6.789%	$42.4273	$42.43	$42.45	$42.40
Purchase #6	$67.50	6.123%	$71.633	$71.63	$71.65	$71.60
Purchase #7	$193.68	3.195%	$199.8681	$199.87	$199.85	$199.90
7 purchase totals =	$944.02		$1,029.4464	$1,029.44	$1,029.50	$1,029.30