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	$96.30	8.561%	$104.5442	$104.54	$104.55	$104.50
Purchase #2	$28.33	10.413%	$31.28	$31.28	$31.30	$31.30
Purchase #3	$140.48	4.172%	$146.3408	$146.34	$146.35	$146.30
Purchase #4	$231.35	7.808%	$249.4138	$249.41	$249.40	$249.40
Purchase #5	$85.97	3.653%	$89.1105	$89.11	$89.10	$89.10
Purchase #6	$198.56	3.540%	$205.589	$205.59	$205.60	$205.60
Purchase #7	$10.37	13.363%	$11.7557	$11.76	$11.75	$11.80
7 purchase totals =	$791.36		$838.0340	$838.03	$838.05	$838.00