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	$229.77	13.185%	$260.0652	$260.07	$260.05	$260.10
Purchase #2	$175.28	5.813%	$185.469	$185.47	$185.45	$185.50
Purchase #3	$124.54	5.696%	$131.6338	$131.63	$131.65	$131.60
Purchase #4	$113.56	12.691%	$127.9719	$127.97	$127.95	$128.00
Purchase #5	$89.86	10.535%	$99.3268	$99.33	$99.35	$99.30
Purchase #6	$165.26	6.653%	$176.2547	$176.25	$176.25	$176.30
Purchase #7	$81.32	6.694%	$86.7636	$86.76	$86.75	$86.80
7 purchase totals =	$979.59		$1,067.4850	$1,067.48	$1,067.45	$1,067.60