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	$220.30	8.215%	$238.3976	$238.40	$238.40	$238.40
Purchase #2	$224.92	12.765%	$253.631	$253.63	$253.65	$253.60
Purchase #3	$171.49	12.558%	$193.0257	$193.03	$193.05	$193.00
Purchase #4	$53.67	3.531%	$55.5651	$55.57	$55.55	$55.60
Purchase #5	$59.39	10.761%	$65.781	$65.78	$65.80	$65.80
Purchase #6	$140.94	10.616%	$155.9022	$155.90	$155.90	$155.90
Purchase #7	$110.60	11.501%	$123.3201	$123.32	$123.30	$123.30
7 purchase totals =	$981.31		$1,085.6227	$1,085.63	$1,085.65	$1,085.60