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	$206.82	7.874%	$223.105	$223.11	$223.10	$223.10
Purchase #2	$203.99	12.257%	$228.9931	$228.99	$229.00	$229.00
Purchase #3	$28.25	11.334%	$31.4519	$31.45	$31.45	$31.50
Purchase #4	$151.55	13.793%	$172.4533	$172.45	$172.45	$172.50
Purchase #5	$120.37	7.508%	$129.4074	$129.41	$129.40	$129.40
Purchase #6	$149.26	10.214%	$164.5054	$164.51	$164.50	$164.50
Purchase #7	$26.56	6.615%	$28.3169	$28.32	$28.30	$28.30
7 purchase totals =	$886.80		$978.2330	$978.24	$978.20	$978.30