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	$156.90	6.853%	$167.6524	$167.65	$167.65	$167.70
Purchase #2	$145.79	11.446%	$162.4771	$162.48	$162.50	$162.50
Purchase #3	$166.80	5.468%	$175.9206	$175.92	$175.90	$175.90
Purchase #4	$112.53	6.653%	$120.0166	$120.02	$120.00	$120.00
Purchase #5	$212.57	7.637%	$228.804	$228.80	$228.80	$228.80
Purchase #6	$64.65	11.521%	$72.0983	$72.10	$72.10	$72.10
Purchase #7	$86.81	4.632%	$90.831	$90.83	$90.85	$90.80
7 purchase totals =	$946.05		$1,017.8000	$1,017.80	$1,017.80	$1,017.80