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	$113.28	6.290%	$120.4053	$120.41	$120.40	$120.40
Purchase #2	$129.81	13.780%	$147.6978	$147.70	$147.70	$147.70
Purchase #3	$194.37	3.302%	$200.7881	$200.79	$200.80	$200.80
Purchase #4	$222.52	3.183%	$229.6028	$229.60	$229.60	$229.60
Purchase #5	$88.46	4.831%	$92.7335	$92.73	$92.75	$92.70
Purchase #6	$89.56	12.814%	$101.0362	$101.04	$101.05	$101.00
Purchase #7	$81.64	5.338%	$85.9979	$86.00	$86.00	$86.00
7 purchase totals =	$919.64		$978.2616	$978.27	$978.30	$978.20