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	$89.29	8.788%	$97.1368	$97.14	$97.15	$97.10
Purchase #2	$74.69	6.300%	$79.3955	$79.40	$79.40	$79.40
Purchase #3	$233.60	12.693%	$263.2508	$263.25	$263.25	$263.30
Purchase #4	$84.87	11.460%	$94.5961	$94.60	$94.60	$94.60
Purchase #5	$45.28	13.750%	$51.506	$51.51	$51.50	$51.50
Purchase #6	$191.43	6.808%	$204.4626	$204.46	$204.45	$204.50
Purchase #7	$136.31	11.443%	$151.908	$151.91	$151.90	$151.90
7 purchase totals =	$855.47		$942.2558	$942.27	$942.25	$942.30