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	$236.37	7.562%	$254.2443	$254.24	$254.25	$254.20
Purchase #2	$25.39	9.264%	$27.7421	$27.74	$27.75	$27.70
Purchase #3	$226.50	11.802%	$253.2315	$253.23	$253.25	$253.20
Purchase #4	$91.27	6.371%	$97.0848	$97.08	$97.10	$97.10
Purchase #5	$147.45	5.468%	$155.5126	$155.51	$155.50	$155.50
Purchase #6	$70.58	11.781%	$78.895	$78.90	$78.90	$78.90
Purchase #7	$98.40	11.338%	$109.5566	$109.56	$109.55	$109.60
7 purchase totals =	$895.96		$976.2669	$976.26	$976.30	$976.20