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	$98.50	3.497%	$101.9445	$101.94	$101.95	$101.90
Purchase #2	$234.71	12.496%	$264.0394	$264.04	$264.05	$264.00
Purchase #3	$75.27	3.396%	$77.8262	$77.83	$77.85	$77.80
Purchase #4	$148.40	11.788%	$165.8934	$165.89	$165.90	$165.90
Purchase #5	$121.32	7.687%	$130.6459	$130.65	$130.65	$130.60
Purchase #6	$89.60	10.357%	$98.8799	$98.88	$98.90	$98.90
Purchase #7	$235.69	4.157%	$245.4876	$245.49	$245.50	$245.50
7 purchase totals =	$1,003.49		$1,084.7169	$1,084.72	$1,084.80	$1,084.60