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	$174.72	6.225%	$185.5963	$185.60	$185.60	$185.60
Purchase #2	$58.39	4.373%	$60.9434	$60.94	$60.95	$60.90
Purchase #3	$34.33	4.241%	$35.7859	$35.79	$35.80	$35.80
Purchase #4	$167.51	3.347%	$173.1166	$173.12	$173.10	$173.10
Purchase #5	$141.75	8.835%	$154.2736	$154.27	$154.25	$154.30
Purchase #6	$12.73	12.107%	$14.2712	$14.27	$14.25	$14.30
Purchase #7	$200.93	10.778%	$222.5862	$222.59	$222.60	$222.60
7 purchase totals =	$790.36		$846.5732	$846.58	$846.55	$846.60