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	$234.31	4.494%	$244.8399	$244.84	$244.85	$244.80
Purchase #2	$207.50	4.155%	$216.1216	$216.12	$216.10	$216.10
Purchase #3	$171.78	4.159%	$178.9243	$178.92	$178.90	$178.90
Purchase #4	$190.56	4.633%	$199.3886	$199.39	$199.40	$199.40
Purchase #5	$148.57	6.781%	$158.6445	$158.64	$158.65	$158.60
Purchase #6	$83.89	3.519%	$86.8421	$86.84	$86.85	$86.80
Purchase #7	$248.52	10.404%	$274.376	$274.38	$274.40	$274.40
7 purchase totals =	$1,285.13		$1,359.1370	$1,359.13	$1,359.15	$1,359.00