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	$54.95	6.183%	$58.3476	$58.35	$58.35	$58.30
Purchase #2	$235.28	11.682%	$262.7654	$262.77	$262.75	$262.80
Purchase #3	$185.91	7.507%	$199.8663	$199.87	$199.85	$199.90
Purchase #4	$168.35	13.470%	$191.0267	$191.03	$191.05	$191.00
Purchase #5	$87.54	13.139%	$99.0419	$99.04	$99.05	$99.00
Purchase #6	$137.30	9.264%	$150.0195	$150.02	$150.00	$150.00
Purchase #7	$107.77	4.328%	$112.4343	$112.43	$112.45	$112.40
7 purchase totals =	$977.10		$1,073.5017	$1,073.51	$1,073.50	$1,073.40