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	$162.44	8.244%	$175.8316	$175.83	$175.85	$175.80
Purchase #2	$83.52	9.739%	$91.654	$91.65	$91.65	$91.70
Purchase #3	$223.93	4.266%	$233.4829	$233.48	$233.50	$233.50
Purchase #4	$20.86	9.744%	$22.8926	$22.89	$22.90	$22.90
Purchase #5	$5.88	8.117%	$6.3573	$6.36	$6.35	$6.40
Purchase #6	$29.33	9.561%	$32.1342	$32.13	$32.15	$32.10
Purchase #7	$101.60	4.237%	$105.9048	$105.90	$105.90	$105.90
7 purchase totals =	$627.56		$668.2574	$668.24	$668.30	$668.30