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	$68.64	4.506%	$71.7329	$71.73	$71.75	$71.70
Purchase #2	$128.74	6.232%	$136.7631	$136.76	$136.75	$136.80
Purchase #3	$41.63	10.177%	$45.8667	$45.87	$45.85	$45.90
Purchase #4	$46.86	9.185%	$51.1641	$51.16	$51.15	$51.20
Purchase #5	$229.66	4.605%	$240.2358	$240.24	$240.25	$240.20
Purchase #6	$86.40	12.312%	$97.0376	$97.04	$97.05	$97.00
Purchase #7	$138.32	13.150%	$156.5091	$156.51	$156.50	$156.50
7 purchase totals =	$740.25		$799.3093	$799.31	$799.30	$799.30