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	$137.44	5.750%	$145.3428	$145.34	$145.35	$145.30
Purchase #2	$165.88	8.835%	$180.5355	$180.54	$180.55	$180.50
Purchase #3	$212.52	4.233%	$221.516	$221.52	$221.50	$221.50
Purchase #4	$147.75	3.497%	$152.9168	$152.92	$152.90	$152.90
Purchase #5	$54.93	11.539%	$61.2684	$61.27	$61.25	$61.30
Purchase #6	$187.46	13.251%	$212.3003	$212.30	$212.30	$212.30
Purchase #7	$142.86	8.165%	$154.5245	$154.52	$154.50	$154.50
7 purchase totals =	$1,048.84		$1,128.4043	$1,128.41	$1,128.35	$1,128.30