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	$207.49	8.658%	$225.4545	$225.45	$225.45	$225.50
Purchase #2	$173.66	4.461%	$181.407	$181.41	$181.40	$181.40
Purchase #3	$138.30	6.137%	$146.7875	$146.79	$146.80	$146.80
Purchase #4	$209.34	6.699%	$223.3637	$223.36	$223.35	$223.40
Purchase #5	$146.31	6.791%	$156.2459	$156.25	$156.25	$156.20
Purchase #6	$81.58	12.281%	$91.5988	$91.60	$91.60	$91.60
Purchase #7	$25.87	10.483%	$28.582	$28.58	$28.60	$28.60
7 purchase totals =	$982.55		$1,053.4394	$1,053.44	$1,053.45	$1,053.50