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	$45.71	7.415%	$49.0994	$49.10	$49.10	$49.10
Purchase #2	$94.84	4.791%	$99.3838	$99.38	$99.40	$99.40
Purchase #3	$152.73	4.857%	$160.1481	$160.15	$160.15	$160.10
Purchase #4	$144.73	6.826%	$154.6093	$154.61	$154.60	$154.60
Purchase #5	$79.83	8.456%	$86.5804	$86.58	$86.60	$86.60
Purchase #6	$57.92	3.793%	$60.1169	$60.12	$60.10	$60.10
Purchase #7	$135.40	6.401%	$144.067	$144.07	$144.05	$144.10
7 purchase totals =	$711.16		$754.0049	$754.01	$754.00	$754.00