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	$130.28	9.582%	$142.7634	$142.76	$142.75	$142.80
Purchase #2	$93.66	8.612%	$101.726	$101.73	$101.75	$101.70
Purchase #3	$250.78	7.482%	$269.5434	$269.54	$269.55	$269.50
Purchase #4	$81.81	4.642%	$85.6076	$85.61	$85.60	$85.60
Purchase #5	$135.59	10.832%	$150.2771	$150.28	$150.30	$150.30
Purchase #6	$226.95	13.195%	$256.8961	$256.90	$256.90	$256.90
Purchase #7	$139.68	13.276%	$158.2239	$158.22	$158.20	$158.20
7 purchase totals =	$1,058.75		$1,165.0375	$1,165.04	$1,165.05	$1,165.00