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	$92.76	7.501%	$99.7179	$99.72	$99.70	$99.70
Purchase #2	$164.31	10.444%	$181.4705	$181.47	$181.45	$181.50
Purchase #3	$47.93	8.514%	$52.0108	$52.01	$52.00	$52.00
Purchase #4	$93.30	3.317%	$96.3948	$96.39	$96.40	$96.40
Purchase #5	$16.73	7.808%	$18.0363	$18.04	$18.05	$18.00
Purchase #6	$134.45	13.348%	$152.3964	$152.40	$152.40	$152.40
Purchase #7	$204.61	9.776%	$224.6127	$224.61	$224.60	$224.60
7 purchase totals =	$754.09		$824.6394	$824.64	$824.60	$824.60