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	$65.42	10.582%	$72.3427	$72.34	$72.35	$72.30
Purchase #2	$155.61	8.653%	$169.0749	$169.07	$169.05	$169.10
Purchase #3	$100.64	11.301%	$112.0133	$112.01	$112.00	$112.00
Purchase #4	$242.84	12.729%	$273.7511	$273.75	$273.75	$273.80
Purchase #5	$224.86	8.489%	$243.9484	$243.95	$243.95	$243.90
Purchase #6	$140.52	11.229%	$156.299	$156.30	$156.30	$156.30
Purchase #7	$198.42	12.349%	$222.9229	$222.92	$222.90	$222.90
7 purchase totals =	$1,128.31		$1,250.3523	$1,250.34	$1,250.30	$1,250.30