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	$149.45	12.353%	$167.9116	$167.91	$167.90	$167.90
Purchase #2	$179.65	9.116%	$196.0269	$196.03	$196.05	$196.00
Purchase #3	$174.78	9.458%	$191.3107	$191.31	$191.30	$191.30
Purchase #4	$186.29	12.485%	$209.5483	$209.55	$209.55	$209.50
Purchase #5	$55.83	5.118%	$58.6874	$58.69	$58.70	$58.70
Purchase #6	$12.44	7.109%	$13.3244	$13.32	$13.30	$13.30
Purchase #7	$234.73	12.197%	$263.36	$263.36	$263.35	$263.40
7 purchase totals =	$993.17		$1,100.1693	$1,100.17	$1,100.15	$1,100.10