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	$160.75	4.146%	$167.4147	$167.41	$167.40	$167.40
Purchase #2	$61.65	5.408%	$64.984	$64.98	$65.00	$65.00
Purchase #3	$120.28	3.723%	$124.758	$124.76	$124.75	$124.80
Purchase #4	$51.63	5.489%	$54.464	$54.46	$54.45	$54.50
Purchase #5	$62.49	8.384%	$67.7292	$67.73	$67.75	$67.70
Purchase #6	$84.85	5.184%	$89.2486	$89.25	$89.25	$89.20
Purchase #7	$131.88	7.463%	$141.7222	$141.72	$141.70	$141.70
7 purchase totals =	$673.53		$710.3207	$710.31	$710.30	$710.30