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	$194.33	6.288%	$206.5495	$206.55	$206.55	$206.50
Purchase #2	$159.63	3.191%	$164.7238	$164.72	$164.70	$164.70
Purchase #3	$97.44	3.120%	$100.4801	$100.48	$100.50	$100.50
Purchase #4	$129.93	8.814%	$141.382	$141.38	$141.40	$141.40
Purchase #5	$12.67	3.804%	$13.152	$13.15	$13.15	$13.20
Purchase #6	$153.47	3.163%	$158.3243	$158.32	$158.30	$158.30
Purchase #7	$147.29	12.448%	$165.6247	$165.62	$165.60	$165.60
7 purchase totals =	$894.76		$950.2364	$950.22	$950.20	$950.20