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	$224.87	13.597%	$255.4456	$255.45	$255.45	$255.40
Purchase #2	$67.86	10.389%	$74.91	$74.91	$74.90	$74.90
Purchase #3	$248.83	13.123%	$281.484	$281.48	$281.50	$281.50
Purchase #4	$147.95	3.372%	$152.9389	$152.94	$152.95	$152.90
Purchase #5	$174.31	6.286%	$185.2671	$185.27	$185.25	$185.30
Purchase #6	$30.46	11.812%	$34.0579	$34.06	$34.05	$34.10
Purchase #7	$118.45	3.183%	$122.2203	$122.22	$122.20	$122.20
7 purchase totals =	$1,012.73		$1,106.3238	$1,106.33	$1,106.30	$1,106.30