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	$109.27	3.756%	$113.3742	$113.37	$113.35	$113.40
Purchase #2	$224.40	3.559%	$232.3864	$232.39	$232.40	$232.40
Purchase #3	$90.87	4.613%	$95.0618	$95.06	$95.05	$95.10
Purchase #4	$175.79	5.275%	$185.0629	$185.06	$185.05	$185.10
Purchase #5	$45.70	3.138%	$47.1341	$47.13	$47.15	$47.10
Purchase #6	$150.73	3.315%	$155.7267	$155.73	$155.75	$155.70
Purchase #7	$40.81	4.313%	$42.5701	$42.57	$42.55	$42.60
7 purchase totals =	$837.57		$871.3162	$871.31	$871.30	$871.40