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	$248.35	10.474%	$274.3622	$274.36	$274.35	$274.40
Purchase #2	$134.32	10.816%	$148.8481	$148.85	$148.85	$148.80
Purchase #3	$67.43	6.624%	$71.8966	$71.90	$71.90	$71.90
Purchase #4	$117.77	4.486%	$123.0532	$123.05	$123.05	$123.10
Purchase #5	$86.35	4.309%	$90.0708	$90.07	$90.05	$90.10
Purchase #6	$246.72	13.237%	$279.3783	$279.38	$279.40	$279.40
Purchase #7	$180.54	4.359%	$188.4097	$188.41	$188.40	$188.40
7 purchase totals =	$1,081.48		$1,176.0189	$1,176.02	$1,176.00	$1,176.10