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	$234.28	3.799%	$243.1803	$243.18	$243.20	$243.20
Purchase #2	$243.53	4.183%	$253.7169	$253.72	$253.70	$253.70
Purchase #3	$74.60	5.760%	$78.897	$78.90	$78.90	$78.90
Purchase #4	$193.52	12.421%	$217.5571	$217.56	$217.55	$217.60
Purchase #5	$42.94	5.763%	$45.4146	$45.41	$45.40	$45.40
Purchase #6	$51.67	9.415%	$56.5347	$56.53	$56.55	$56.50
Purchase #7	$26.92	13.611%	$30.5841	$30.58	$30.60	$30.60
7 purchase totals =	$867.46		$925.8847	$925.88	$925.90	$925.90