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	$84.41	6.427%	$89.835	$89.84	$89.85	$89.80
Purchase #2	$99.40	7.605%	$106.9594	$106.96	$106.95	$107.00
Purchase #3	$219.97	3.870%	$228.4828	$228.48	$228.50	$228.50
Purchase #4	$87.81	13.625%	$99.7741	$99.77	$99.75	$99.80
Purchase #5	$250.61	5.272%	$263.8222	$263.82	$263.80	$263.80
Purchase #6	$105.43	13.187%	$119.3331	$119.33	$119.35	$119.30
Purchase #7	$220.78	4.414%	$230.5252	$230.53	$230.55	$230.50
7 purchase totals =	$1,068.41		$1,138.7318	$1,138.73	$1,138.75	$1,138.70