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	$204.80	9.303%	$223.8525	$223.85	$223.85	$223.90
Purchase #2	$72.46	5.702%	$76.5917	$76.59	$76.60	$76.60
Purchase #3	$156.32	6.739%	$166.8544	$166.85	$166.85	$166.90
Purchase #4	$243.25	13.162%	$275.2666	$275.27	$275.25	$275.30
Purchase #5	$181.72	7.431%	$195.2236	$195.22	$195.20	$195.20
Purchase #6	$82.53	12.822%	$93.112	$93.11	$93.10	$93.10
Purchase #7	$113.81	10.396%	$125.6417	$125.64	$125.65	$125.60
7 purchase totals =	$1,054.89		$1,156.5425	$1,156.53	$1,156.50	$1,156.60