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	$92.28	7.474%	$99.177	$99.18	$99.20	$99.20
Purchase #2	$67.65	5.131%	$71.1211	$71.12	$71.10	$71.10
Purchase #3	$136.57	4.629%	$142.8918	$142.89	$142.90	$142.90
Purchase #4	$40.43	3.437%	$41.8196	$41.82	$41.80	$41.80
Purchase #5	$241.71	5.515%	$255.0403	$255.04	$255.05	$255.00
Purchase #6	$57.49	13.492%	$65.2466	$65.25	$65.25	$65.20
Purchase #7	$88.71	8.614%	$96.3515	$96.35	$96.35	$96.40
7 purchase totals =	$724.84		$771.6479	$771.65	$771.65	$771.60