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	$219.50	6.788%	$234.3997	$234.40	$234.40	$234.40
Purchase #2	$160.57	12.348%	$180.3972	$180.40	$180.40	$180.40
Purchase #3	$30.56	10.789%	$33.8571	$33.86	$33.85	$33.90
Purchase #4	$215.44	11.780%	$240.8188	$240.82	$240.80	$240.80
Purchase #5	$243.26	9.297%	$265.8759	$265.88	$265.90	$265.90
Purchase #6	$52.47	13.771%	$59.6956	$59.70	$59.70	$59.70
Purchase #7	$143.41	6.728%	$153.0586	$153.06	$153.05	$153.10
7 purchase totals =	$1,065.21		$1,168.1029	$1,168.12	$1,168.10	$1,168.20