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	$162.74	4.235%	$169.632	$169.63	$169.65	$169.60
Purchase #2	$133.46	12.548%	$150.2066	$150.21	$150.20	$150.20
Purchase #3	$77.38	7.107%	$82.8794	$82.88	$82.90	$82.90
Purchase #4	$176.38	13.331%	$199.8932	$199.89	$199.90	$199.90
Purchase #5	$203.91	12.820%	$230.0513	$230.05	$230.05	$230.10
Purchase #6	$162.32	3.251%	$167.597	$167.60	$167.60	$167.60
Purchase #7	$139.83	11.704%	$156.1957	$156.20	$156.20	$156.20
7 purchase totals =	$1,056.02		$1,156.4552	$1,156.46	$1,156.50	$1,156.50