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	$78.34	8.533%	$85.0248	$85.02	$85.00	$85.00
Purchase #2	$231.32	5.360%	$243.7188	$243.72	$243.70	$243.70
Purchase #3	$186.33	3.195%	$192.2832	$192.28	$192.30	$192.30
Purchase #4	$99.45	11.730%	$111.1155	$111.12	$111.10	$111.10
Purchase #5	$228.73	6.395%	$243.3573	$243.36	$243.35	$243.40
Purchase #6	$150.29	9.173%	$164.0761	$164.08	$164.10	$164.10
Purchase #7	$147.67	8.738%	$160.5734	$160.57	$160.55	$160.60
7 purchase totals =	$1,122.13		$1,200.1491	$1,200.15	$1,200.10	$1,200.20