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	$57.60	3.510%	$59.6218	$59.62	$59.60	$59.60
Purchase #2	$222.76	6.463%	$237.157	$237.16	$237.15	$237.20
Purchase #3	$174.91	9.755%	$191.9725	$191.97	$191.95	$192.00
Purchase #4	$133.56	8.777%	$145.2826	$145.28	$145.30	$145.30
Purchase #5	$42.30	10.638%	$46.7999	$46.80	$46.80	$46.80
Purchase #6	$161.59	3.747%	$167.6448	$167.64	$167.65	$167.60
Purchase #7	$94.55	8.287%	$102.3854	$102.39	$102.40	$102.40
7 purchase totals =	$887.27		$950.8640	$950.86	$950.85	$950.90