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	$165.61	4.711%	$173.4119	$173.41	$173.40	$173.40
Purchase #2	$28.88	13.709%	$32.8392	$32.84	$32.85	$32.80
Purchase #3	$40.83	9.300%	$44.6272	$44.63	$44.65	$44.60
Purchase #4	$153.82	12.678%	$173.3213	$173.32	$173.30	$173.30
Purchase #5	$90.79	8.363%	$98.3828	$98.38	$98.40	$98.40
Purchase #6	$250.88	11.771%	$280.4111	$280.41	$280.40	$280.40
Purchase #7	$68.83	3.588%	$71.2996	$71.30	$71.30	$71.30
7 purchase totals =	$799.64		$874.2931	$874.29	$874.30	$874.20