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	$96.44	7.653%	$103.8206	$103.82	$103.80	$103.80
Purchase #2	$101.77	7.149%	$109.0455	$109.05	$109.05	$109.00
Purchase #3	$130.26	3.345%	$134.6172	$134.62	$134.60	$134.60
Purchase #4	$239.30	3.454%	$247.5654	$247.57	$247.55	$247.60
Purchase #5	$78.76	11.296%	$87.6567	$87.66	$87.65	$87.70
Purchase #6	$142.66	11.110%	$158.5095	$158.51	$158.50	$158.50
Purchase #7	$65.32	11.641%	$72.9239	$72.92	$72.90	$72.90
7 purchase totals =	$854.51		$914.1388	$914.15	$914.05	$914.10