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	$163.95	9.382%	$179.3318	$179.33	$179.35	$179.30
Purchase #2	$28.52	5.113%	$29.9782	$29.98	$30.00	$30.00
Purchase #3	$55.70	6.827%	$59.5026	$59.50	$59.50	$59.50
Purchase #4	$81.35	9.871%	$89.3801	$89.38	$89.40	$89.40
Purchase #5	$12.99	11.176%	$14.4418	$14.44	$14.45	$14.40
Purchase #6	$99.73	10.690%	$110.3911	$110.39	$110.40	$110.40
Purchase #7	$60.81	11.650%	$67.8944	$67.89	$67.90	$67.90
7 purchase totals =	$503.05		$550.9200	$550.91	$551.00	$550.90