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	$162.31	3.354%	$167.7539	$167.75	$167.75	$167.80
Purchase #2	$212.81	12.265%	$238.9111	$238.91	$238.90	$238.90
Purchase #3	$193.76	11.593%	$216.2226	$216.22	$216.20	$216.20
Purchase #4	$142.36	7.138%	$152.5217	$152.52	$152.50	$152.50
Purchase #5	$209.69	5.810%	$221.873	$221.87	$221.85	$221.90
Purchase #6	$102.80	8.108%	$111.135	$111.14	$111.15	$111.10
Purchase #7	$228.28	4.190%	$237.8449	$237.84	$237.85	$237.80
7 purchase totals =	$1,252.01		$1,346.2622	$1,346.25	$1,346.20	$1,346.20