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	$186.77	7.258%	$200.3258	$200.33	$200.35	$200.30
Purchase #2	$205.47	6.461%	$218.7454	$218.75	$218.75	$218.70
Purchase #3	$98.56	5.670%	$104.1484	$104.15	$104.15	$104.10
Purchase #4	$167.82	4.261%	$174.9708	$174.97	$174.95	$175.00
Purchase #5	$53.98	11.231%	$60.0425	$60.04	$60.05	$60.00
Purchase #6	$175.60	5.826%	$185.8305	$185.83	$185.85	$185.80
Purchase #7	$200.60	12.175%	$225.0231	$225.02	$225.00	$225.00
7 purchase totals =	$1,088.80		$1,169.0865	$1,169.09	$1,169.10	$1,168.90