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	$233.63	12.829%	$263.6024	$263.60	$263.60	$263.60
Purchase #2	$225.60	4.737%	$236.2867	$236.29	$236.30	$236.30
Purchase #3	$229.55	11.383%	$255.6797	$255.68	$255.70	$255.70
Purchase #4	$141.84	12.700%	$159.8537	$159.85	$159.85	$159.90
Purchase #5	$58.72	6.386%	$62.4699	$62.47	$62.45	$62.50
Purchase #6	$92.42	11.743%	$103.2729	$103.27	$103.25	$103.30
Purchase #7	$245.57	10.154%	$270.5052	$270.51	$270.50	$270.50
7 purchase totals =	$1,227.33		$1,351.6705	$1,351.67	$1,351.65	$1,351.80