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	$191.29	4.612%	$200.1123	$200.11	$200.10	$200.10
Purchase #2	$76.34	4.839%	$80.0341	$80.03	$80.05	$80.00
Purchase #3	$70.31	4.363%	$73.3776	$73.38	$73.40	$73.40
Purchase #4	$84.74	12.645%	$95.4554	$95.46	$95.45	$95.50
Purchase #5	$185.92	12.200%	$208.6022	$208.60	$208.60	$208.60
Purchase #6	$133.82	10.551%	$147.9393	$147.94	$147.95	$147.90
Purchase #7	$173.52	9.675%	$190.3081	$190.31	$190.30	$190.30
7 purchase totals =	$915.94		$995.8290	$995.83	$995.85	$995.80