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	$176.27	6.586%	$187.8791	$187.88	$187.90	$187.90
Purchase #2	$84.67	11.727%	$94.5993	$94.60	$94.60	$94.60
Purchase #3	$36.49	11.643%	$40.7385	$40.74	$40.75	$40.70
Purchase #4	$238.64	6.136%	$253.283	$253.28	$253.30	$253.30
Purchase #5	$111.79	10.279%	$123.2809	$123.28	$123.30	$123.30
Purchase #6	$105.70	3.262%	$109.1479	$109.15	$109.15	$109.10
Purchase #7	$111.77	5.323%	$117.7195	$117.72	$117.70	$117.70
7 purchase totals =	$865.33		$926.6482	$926.65	$926.70	$926.60