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	$206.38	11.358%	$229.8206	$229.82	$229.80	$229.80
Purchase #2	$138.57	12.565%	$155.9813	$155.98	$156.00	$156.00
Purchase #3	$76.93	4.135%	$80.1111	$80.11	$80.10	$80.10
Purchase #4	$82.48	8.711%	$89.6648	$89.66	$89.65	$89.70
Purchase #5	$107.37	8.700%	$116.7112	$116.71	$116.70	$116.70
Purchase #6	$206.49	7.662%	$222.3113	$222.31	$222.30	$222.30
Purchase #7	$159.75	7.695%	$172.0428	$172.04	$172.05	$172.00
7 purchase totals =	$977.97		$1,066.6431	$1,066.63	$1,066.60	$1,066.60