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	$178.56	9.481%	$195.4893	$195.49	$195.50	$195.50
Purchase #2	$127.64	11.508%	$142.3288	$142.33	$142.35	$142.30
Purchase #3	$247.80	12.337%	$278.3711	$278.37	$278.35	$278.40
Purchase #4	$66.87	6.746%	$71.3811	$71.38	$71.40	$71.40
Purchase #5	$96.87	3.802%	$100.553	$100.55	$100.55	$100.60
Purchase #6	$12.29	9.721%	$13.4847	$13.48	$13.50	$13.50
Purchase #7	$238.37	13.743%	$271.1292	$271.13	$271.15	$271.10
7 purchase totals =	$968.40		$1,072.7372	$1,072.73	$1,072.80	$1,072.80