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	$98.78	12.744%	$111.3685	$111.37	$111.35	$111.40
Purchase #2	$197.37	9.747%	$216.6077	$216.61	$216.60	$216.60
Purchase #3	$26.29	9.391%	$28.7589	$28.76	$28.75	$28.80
Purchase #4	$238.96	12.597%	$269.0618	$269.06	$269.05	$269.10
Purchase #5	$18.66	8.813%	$20.3045	$20.30	$20.30	$20.30
Purchase #6	$72.47	11.378%	$80.7156	$80.72	$80.70	$80.70
Purchase #7	$196.93	4.567%	$205.9238	$205.92	$205.90	$205.90
7 purchase totals =	$849.46		$932.7408	$932.74	$932.65	$932.80