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	$57.73	5.119%	$60.6852	$60.69	$60.70	$60.70
Purchase #2	$49.33	11.797%	$55.1495	$55.15	$55.15	$55.10
Purchase #3	$209.92	8.258%	$227.2552	$227.26	$227.25	$227.30
Purchase #4	$246.80	7.532%	$265.389	$265.39	$265.40	$265.40
Purchase #5	$244.72	12.710%	$275.8239	$275.82	$275.80	$275.80
Purchase #6	$126.25	7.274%	$135.4334	$135.43	$135.45	$135.40
Purchase #7	$74.39	5.583%	$78.5432	$78.54	$78.55	$78.50
7 purchase totals =	$1,009.14		$1,098.2794	$1,098.28	$1,098.30	$1,098.20