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	$89.73	11.190%	$99.7708	$99.77	$99.75	$99.80
Purchase #2	$160.58	12.806%	$181.1439	$181.14	$181.15	$181.10
Purchase #3	$184.83	9.404%	$202.2114	$202.21	$202.20	$202.20
Purchase #4	$43.36	8.309%	$46.9628	$46.96	$46.95	$47.00
Purchase #5	$73.79	6.402%	$78.514	$78.51	$78.50	$78.50
Purchase #6	$59.95	4.653%	$62.7395	$62.74	$62.75	$62.70
Purchase #7	$240.59	11.824%	$269.0374	$269.04	$269.05	$269.00
7 purchase totals =	$852.83		$940.3798	$940.37	$940.35	$940.30