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	$171.59	11.136%	$190.6983	$190.70	$190.70	$190.70
Purchase #2	$102.40	6.566%	$109.1236	$109.12	$109.10	$109.10
Purchase #3	$177.88	8.756%	$193.4552	$193.46	$193.45	$193.50
Purchase #4	$95.34	10.337%	$105.1953	$105.20	$105.20	$105.20
Purchase #5	$143.35	11.610%	$159.9929	$159.99	$160.00	$160.00
Purchase #6	$174.73	10.686%	$193.4016	$193.40	$193.40	$193.40
Purchase #7	$145.25	9.794%	$159.4758	$159.48	$159.50	$159.50
7 purchase totals =	$1,010.54		$1,111.3427	$1,111.35	$1,111.35	$1,111.40