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	$119.73	12.575%	$134.786	$134.79	$134.80	$134.80
Purchase #2	$97.81	6.230%	$103.9036	$103.90	$103.90	$103.90
Purchase #3	$203.35	9.679%	$223.0322	$223.03	$223.05	$223.00
Purchase #4	$117.71	11.562%	$131.3196	$131.32	$131.30	$131.30
Purchase #5	$117.42	8.588%	$127.504	$127.50	$127.50	$127.50
Purchase #6	$46.49	5.210%	$48.9121	$48.91	$48.90	$48.90
Purchase #7	$241.68	3.668%	$250.5448	$250.54	$250.55	$250.50
7 purchase totals =	$944.19		$1,020.0023	$1,019.99	$1,020.00	$1,019.90