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	$179.32	7.662%	$193.0595	$193.06	$193.05	$193.10
Purchase #2	$160.64	13.656%	$182.577	$182.58	$182.60	$182.60
Purchase #3	$87.37	13.754%	$99.3869	$99.39	$99.40	$99.40
Purchase #4	$35.89	4.437%	$37.4824	$37.48	$37.50	$37.50
Purchase #5	$172.84	4.434%	$180.5037	$180.50	$180.50	$180.50
Purchase #6	$29.50	12.413%	$33.1618	$33.16	$33.15	$33.20
Purchase #7	$46.76	6.789%	$49.9345	$49.93	$49.95	$49.90
7 purchase totals =	$712.32		$776.1058	$776.10	$776.15	$776.20