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	$75.75	13.183%	$85.7361	$85.74	$85.75	$85.70
Purchase #2	$26.32	9.511%	$28.8233	$28.82	$28.80	$28.80
Purchase #3	$78.84	9.715%	$86.4993	$86.50	$86.50	$86.50
Purchase #4	$160.94	6.555%	$171.4896	$171.49	$171.50	$171.50
Purchase #5	$160.58	9.162%	$175.2923	$175.29	$175.30	$175.30
Purchase #6	$99.71	6.404%	$106.0954	$106.10	$106.10	$106.10
Purchase #7	$213.54	9.392%	$233.5957	$233.60	$233.60	$233.60
7 purchase totals =	$815.68		$887.5317	$887.54	$887.55	$887.50