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	$225.93	10.761%	$250.2423	$250.24	$250.25	$250.20
Purchase #2	$169.31	6.346%	$180.0544	$180.05	$180.05	$180.10
Purchase #3	$136.43	8.425%	$147.9242	$147.92	$147.90	$147.90
Purchase #4	$187.52	13.354%	$212.5614	$212.56	$212.55	$212.60
Purchase #5	$134.53	4.830%	$141.0278	$141.03	$141.05	$141.00
Purchase #6	$31.35	3.126%	$32.33	$32.33	$32.35	$32.30
Purchase #7	$57.65	3.796%	$59.8384	$59.84	$59.85	$59.80
7 purchase totals =	$942.72		$1,023.9785	$1,023.97	$1,024.00	$1,023.90