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	$168.71	5.345%	$177.7275	$177.73	$177.75	$177.70
Purchase #2	$168.66	7.642%	$181.549	$181.55	$181.55	$181.50
Purchase #3	$82.73	4.208%	$86.2113	$86.21	$86.20	$86.20
Purchase #4	$9.86	10.449%	$10.8903	$10.89	$10.90	$10.90
Purchase #5	$31.81	4.165%	$33.1349	$33.13	$33.15	$33.10
Purchase #6	$30.74	5.802%	$32.5235	$32.52	$32.50	$32.50
Purchase #7	$91.88	11.458%	$102.4076	$102.41	$102.40	$102.40
7 purchase totals =	$584.39		$624.4441	$624.44	$624.45	$624.30