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	$88.68	6.111%	$94.0992	$94.10	$94.10	$94.10
Purchase #2	$17.89	6.437%	$19.0416	$19.04	$19.05	$19.00
Purchase #3	$48.53	12.444%	$54.5691	$54.57	$54.55	$54.60
Purchase #4	$56.30	5.323%	$59.2968	$59.30	$59.30	$59.30
Purchase #5	$34.95	9.829%	$38.3852	$38.39	$38.40	$38.40
Purchase #6	$16.39	12.568%	$18.4499	$18.45	$18.45	$18.40
Purchase #7	$198.59	7.655%	$213.7921	$213.79	$213.80	$213.80
7 purchase totals =	$461.33		$497.6339	$497.64	$497.65	$497.60