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	$215.61	12.352%	$242.2421	$242.24	$242.25	$242.20
Purchase #2	$39.70	10.693%	$43.9451	$43.95	$43.95	$43.90
Purchase #3	$30.85	6.412%	$32.8281	$32.83	$32.85	$32.80
Purchase #4	$70.27	11.404%	$78.2836	$78.28	$78.30	$78.30
Purchase #5	$222.70	4.581%	$232.9019	$232.90	$232.90	$232.90
Purchase #6	$170.86	12.168%	$191.6502	$191.65	$191.65	$191.70
Purchase #7	$227.71	10.464%	$251.5376	$251.54	$251.55	$251.50
7 purchase totals =	$977.70		$1,073.3886	$1,073.39	$1,073.45	$1,073.30