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	$225.44	5.404%	$237.6228	$237.62	$237.60	$237.60
Purchase #2	$174.40	11.741%	$194.8763	$194.88	$194.90	$194.90
Purchase #3	$74.70	10.183%	$82.3067	$82.31	$82.30	$82.30
Purchase #4	$137.66	7.857%	$148.4759	$148.48	$148.50	$148.50
Purchase #5	$129.72	7.457%	$139.3932	$139.39	$139.40	$139.40
Purchase #6	$126.99	11.477%	$141.5646	$141.56	$141.55	$141.60
Purchase #7	$228.41	5.150%	$240.1731	$240.17	$240.15	$240.20
7 purchase totals =	$1,097.32		$1,184.4126	$1,184.41	$1,184.40	$1,184.50