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	$91.77	6.870%	$98.0746	$98.07	$98.05	$98.10
Purchase #2	$237.59	11.351%	$264.5588	$264.56	$264.55	$264.60
Purchase #3	$233.43	12.572%	$262.7768	$262.78	$262.80	$262.80
Purchase #4	$224.28	10.709%	$248.2981	$248.30	$248.30	$248.30
Purchase #5	$40.33	4.609%	$42.1888	$42.19	$42.20	$42.20
Purchase #6	$220.33	5.754%	$233.0078	$233.01	$233.00	$233.00
Purchase #7	$103.72	11.248%	$115.3864	$115.39	$115.40	$115.40
7 purchase totals =	$1,151.45		$1,264.2913	$1,264.30	$1,264.30	$1,264.40