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	$169.88	7.353%	$182.3713	$182.37	$182.35	$182.40
Purchase #2	$94.82	6.348%	$100.8392	$100.84	$100.85	$100.80
Purchase #3	$155.70	3.234%	$160.7353	$160.74	$160.75	$160.70
Purchase #4	$223.29	12.181%	$250.489	$250.49	$250.50	$250.50
Purchase #5	$222.58	7.134%	$238.4589	$238.46	$238.45	$238.50
Purchase #6	$81.55	10.259%	$89.9162	$89.92	$89.90	$89.90
Purchase #7	$77.46	9.287%	$84.6537	$84.65	$84.65	$84.70
7 purchase totals =	$1,025.28		$1,107.4636	$1,107.47	$1,107.45	$1,107.50