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	$91.34	7.482%	$98.1741	$98.17	$98.15	$98.20
Purchase #2	$76.32	5.407%	$80.4466	$80.45	$80.45	$80.40
Purchase #3	$16.39	11.839%	$18.3304	$18.33	$18.35	$18.30
Purchase #4	$222.83	8.427%	$241.6079	$241.61	$241.60	$241.60
Purchase #5	$140.90	4.615%	$147.4025	$147.40	$147.40	$147.40
Purchase #6	$71.76	5.501%	$75.7075	$75.71	$75.70	$75.70
Purchase #7	$96.78	3.406%	$100.0763	$100.08	$100.10	$100.10
7 purchase totals =	$716.32		$761.7453	$761.75	$761.75	$761.70