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	$142.98	9.680%	$156.8205	$156.82	$156.80	$156.80
Purchase #2	$48.42	11.286%	$53.8847	$53.88	$53.90	$53.90
Purchase #3	$33.28	12.172%	$37.3308	$37.33	$37.35	$37.30
Purchase #4	$97.49	11.319%	$108.5249	$108.52	$108.50	$108.50
Purchase #5	$25.31	8.352%	$27.4239	$27.42	$27.40	$27.40
Purchase #6	$211.85	7.250%	$227.2091	$227.21	$227.20	$227.20
Purchase #7	$193.62	10.494%	$213.9385	$213.94	$213.95	$213.90
7 purchase totals =	$752.95		$825.1324	$825.12	$825.10	$825.00