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	$16.26	9.149%	$17.7476	$17.75	$17.75	$17.70
Purchase #2	$247.94	10.284%	$273.4381	$273.44	$273.45	$273.40
Purchase #3	$179.74	11.525%	$200.455	$200.46	$200.45	$200.50
Purchase #4	$20.33	10.830%	$22.5317	$22.53	$22.55	$22.50
Purchase #5	$181.91	12.829%	$205.2472	$205.25	$205.25	$205.20
Purchase #6	$243.83	10.851%	$270.288	$270.29	$270.30	$270.30
Purchase #7	$73.27	7.693%	$78.9067	$78.91	$78.90	$78.90
7 purchase totals =	$963.28		$1,068.6143	$1,068.63	$1,068.65	$1,068.50