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	$192.37	8.669%	$209.0466	$209.05	$209.05	$209.00
Purchase #2	$33.98	13.241%	$38.4793	$38.48	$38.50	$38.50
Purchase #3	$173.77	5.550%	$183.4142	$183.41	$183.40	$183.40
Purchase #4	$221.37	9.560%	$242.533	$242.53	$242.55	$242.50
Purchase #5	$78.56	12.437%	$88.3305	$88.33	$88.35	$88.30
Purchase #6	$235.80	12.328%	$264.8694	$264.87	$264.85	$264.90
Purchase #7	$164.94	12.533%	$185.6119	$185.61	$185.60	$185.60
7 purchase totals =	$1,100.79		$1,212.2849	$1,212.28	$1,212.30	$1,212.20