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	$227.47	7.657%	$244.8874	$244.89	$244.90	$244.90
Purchase #2	$14.67	9.573%	$16.0744	$16.07	$16.05	$16.10
Purchase #3	$106.72	4.518%	$111.5416	$111.54	$111.55	$111.50
Purchase #4	$98.92	10.775%	$109.5786	$109.58	$109.60	$109.60
Purchase #5	$131.47	6.793%	$140.4008	$140.40	$140.40	$140.40
Purchase #6	$196.62	9.580%	$215.4562	$215.46	$215.45	$215.50
Purchase #7	$70.71	8.596%	$76.7882	$76.79	$76.80	$76.80
7 purchase totals =	$846.58		$914.7272	$914.73	$914.75	$914.80