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	$44.64	4.159%	$46.4966	$46.50	$46.50	$46.50
Purchase #2	$174.34	9.731%	$191.305	$191.31	$191.30	$191.30
Purchase #3	$38.33	9.833%	$42.099	$42.10	$42.10	$42.10
Purchase #4	$78.85	12.694%	$88.8592	$88.86	$88.85	$88.90
Purchase #5	$169.63	9.218%	$185.2665	$185.27	$185.25	$185.30
Purchase #6	$58.46	12.583%	$65.816	$65.82	$65.80	$65.80
Purchase #7	$166.95	8.863%	$181.7468	$181.75	$181.75	$181.70
7 purchase totals =	$731.20		$801.5891	$801.61	$801.55	$801.60