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	$245.67	3.140%	$253.384	$253.38	$253.40	$253.40
Purchase #2	$75.36	3.438%	$77.9509	$77.95	$77.95	$78.00
Purchase #3	$136.88	5.424%	$144.3044	$144.30	$144.30	$144.30
Purchase #4	$19.88	10.106%	$21.8891	$21.89	$21.90	$21.90
Purchase #5	$138.65	9.668%	$152.0547	$152.05	$152.05	$152.10
Purchase #6	$250.49	3.681%	$259.7105	$259.71	$259.70	$259.70
Purchase #7	$165.39	5.744%	$174.89	$174.89	$174.90	$174.90
7 purchase totals =	$1,032.32		$1,084.1836	$1,084.17	$1,084.20	$1,084.30