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	$37.33	3.816%	$38.7545	$38.75	$38.75	$38.80
Purchase #2	$58.39	3.401%	$60.3758	$60.38	$60.40	$60.40
Purchase #3	$76.90	11.408%	$85.6728	$85.67	$85.65	$85.70
Purchase #4	$17.85	9.817%	$19.6023	$19.60	$19.60	$19.60
Purchase #5	$50.44	10.599%	$55.7861	$55.79	$55.80	$55.80
Purchase #6	$53.98	7.195%	$57.8639	$57.86	$57.85	$57.90
Purchase #7	$47.33	10.471%	$52.2859	$52.29	$52.30	$52.30
7 purchase totals =	$342.22		$370.3413	$370.34	$370.35	$370.50