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	$92.55	7.418%	$99.4154	$99.42	$99.40	$99.40
Purchase #2	$225.29	10.350%	$248.6075	$248.61	$248.60	$248.60
Purchase #3	$151.31	11.203%	$168.2613	$168.26	$168.25	$168.30
Purchase #4	$41.85	10.540%	$46.261	$46.26	$46.25	$46.30
Purchase #5	$220.69	4.151%	$229.8508	$229.85	$229.85	$229.90
Purchase #6	$82.58	13.827%	$93.9983	$94.00	$94.00	$94.00
Purchase #7	$152.42	12.139%	$170.9223	$170.92	$170.90	$170.90
7 purchase totals =	$966.69		$1,057.3166	$1,057.32	$1,057.25	$1,057.40