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	$212.40	5.420%	$223.9121	$223.91	$223.90	$223.90
Purchase #2	$175.72	11.236%	$195.4639	$195.46	$195.45	$195.50
Purchase #3	$104.89	13.496%	$119.046	$119.05	$119.05	$119.00
Purchase #4	$193.50	3.747%	$200.7504	$200.75	$200.75	$200.80
Purchase #5	$217.53	10.156%	$239.6223	$239.62	$239.60	$239.60
Purchase #6	$199.33	12.347%	$223.9413	$223.94	$223.95	$223.90
Purchase #7	$250.35	7.284%	$268.5855	$268.59	$268.60	$268.60
7 purchase totals =	$1,353.72		$1,471.3215	$1,471.32	$1,471.30	$1,471.30