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	$74.32	12.219%	$83.4012	$83.40	$83.40	$83.40
Purchase #2	$227.61	11.353%	$253.4506	$253.45	$253.45	$253.50
Purchase #3	$166.74	11.282%	$185.5516	$185.55	$185.55	$185.60
Purchase #4	$74.44	9.661%	$81.6316	$81.63	$81.65	$81.60
Purchase #5	$154.49	13.342%	$175.1021	$175.10	$175.10	$175.10
Purchase #6	$140.78	5.713%	$148.8228	$148.82	$148.80	$148.80
Purchase #7	$237.39	13.258%	$268.8632	$268.86	$268.85	$268.90
7 purchase totals =	$1,075.77		$1,196.8231	$1,196.81	$1,196.80	$1,196.90