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	$174.96	9.357%	$191.331	$191.33	$191.35	$191.30
Purchase #2	$142.95	7.760%	$154.0429	$154.04	$154.05	$154.00
Purchase #3	$58.48	13.441%	$66.3403	$66.34	$66.35	$66.30
Purchase #4	$156.31	12.374%	$175.6518	$175.65	$175.65	$175.70
Purchase #5	$89.90	13.738%	$102.2505	$102.25	$102.25	$102.30
Purchase #6	$76.35	9.358%	$83.4948	$83.49	$83.50	$83.50
Purchase #7	$225.56	13.346%	$255.6632	$255.66	$255.65	$255.70
7 purchase totals =	$924.51		$1,028.7745	$1,028.76	$1,028.80	$1,028.80