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	$172.72	11.449%	$192.4947	$192.49	$192.50	$192.50
Purchase #2	$117.80	10.117%	$129.7178	$129.72	$129.70	$129.70
Purchase #3	$230.69	10.410%	$254.7048	$254.70	$254.70	$254.70
Purchase #4	$98.54	4.443%	$102.9181	$102.92	$102.90	$102.90
Purchase #5	$59.72	10.253%	$65.8431	$65.84	$65.85	$65.80
Purchase #6	$205.52	6.274%	$218.4143	$218.41	$218.40	$218.40
Purchase #7	$39.88	7.530%	$42.883	$42.88	$42.90	$42.90
7 purchase totals =	$924.87		$1,006.9758	$1,006.96	$1,006.95	$1,006.90