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	$150.66	12.358%	$169.2786	$169.28	$169.30	$169.30
Purchase #2	$203.26	3.589%	$210.555	$210.56	$210.55	$210.60
Purchase #3	$54.25	9.816%	$59.5752	$59.58	$59.60	$59.60
Purchase #4	$229.71	13.261%	$260.1718	$260.17	$260.15	$260.20
Purchase #5	$125.97	13.412%	$142.8651	$142.87	$142.85	$142.90
Purchase #6	$197.96	12.656%	$223.0138	$223.01	$223.00	$223.00
Purchase #7	$200.37	7.565%	$215.528	$215.53	$215.55	$215.50
7 purchase totals =	$1,162.18		$1,280.9875	$1,281.00	$1,281.00	$1,281.10