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	$216.96	4.367%	$226.4346	$226.43	$226.45	$226.40
Purchase #2	$133.28	8.660%	$144.822	$144.82	$144.80	$144.80
Purchase #3	$136.39	7.302%	$146.3492	$146.35	$146.35	$146.30
Purchase #4	$82.45	4.435%	$86.1067	$86.11	$86.10	$86.10
Purchase #5	$56.26	5.139%	$59.1512	$59.15	$59.15	$59.20
Purchase #6	$79.84	12.629%	$89.923	$89.92	$89.90	$89.90
Purchase #7	$77.69	13.669%	$88.3094	$88.31	$88.30	$88.30
7 purchase totals =	$782.87		$841.0961	$841.09	$841.05	$841.00