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	$185.99	4.373%	$194.1233	$194.12	$194.10	$194.10
Purchase #2	$143.88	5.711%	$152.097	$152.10	$152.10	$152.10
Purchase #3	$79.86	12.178%	$89.5854	$89.59	$89.60	$89.60
Purchase #4	$224.67	6.135%	$238.4535	$238.45	$238.45	$238.50
Purchase #5	$26.80	11.560%	$29.8981	$29.90	$29.90	$29.90
Purchase #6	$34.69	5.729%	$36.6774	$36.68	$36.70	$36.70
Purchase #7	$234.87	11.675%	$262.2911	$262.29	$262.30	$262.30
7 purchase totals =	$930.76		$1,003.1258	$1,003.13	$1,003.15	$1,003.20