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	$169.84	6.443%	$180.7828	$180.78	$180.80	$180.80
Purchase #2	$123.56	10.309%	$136.2978	$136.30	$136.30	$136.30
Purchase #3	$139.29	9.712%	$152.8178	$152.82	$152.80	$152.80
Purchase #4	$151.29	3.705%	$156.8953	$156.90	$156.90	$156.90
Purchase #5	$125.33	3.412%	$129.6063	$129.61	$129.60	$129.60
Purchase #6	$46.49	5.188%	$48.9019	$48.90	$48.90	$48.90
Purchase #7	$197.34	7.442%	$212.026	$212.03	$212.05	$212.00
7 purchase totals =	$953.14		$1,017.3279	$1,017.34	$1,017.35	$1,017.30