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	$13.29	10.442%	$14.6777	$14.68	$14.70	$14.70
Purchase #2	$212.25	13.184%	$240.233	$240.23	$240.25	$240.20
Purchase #3	$200.64	4.315%	$209.2976	$209.30	$209.30	$209.30
Purchase #4	$133.63	10.287%	$147.3765	$147.38	$147.40	$147.40
Purchase #5	$146.54	12.272%	$164.5234	$164.52	$164.50	$164.50
Purchase #6	$233.65	4.311%	$243.7227	$243.72	$243.70	$243.70
Purchase #7	$117.78	11.209%	$130.982	$130.98	$131.00	$131.00
7 purchase totals =	$1,057.78		$1,150.8129	$1,150.81	$1,150.85	$1,150.80