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	$119.69	6.274%	$127.1994	$127.20	$127.20	$127.20
Purchase #2	$218.72	10.681%	$242.0815	$242.08	$242.10	$242.10
Purchase #3	$236.32	8.586%	$256.6104	$256.61	$256.60	$256.60
Purchase #4	$170.47	12.526%	$191.8231	$191.82	$191.80	$191.80
Purchase #5	$89.70	8.444%	$97.2743	$97.27	$97.25	$97.30
Purchase #6	$96.56	13.721%	$109.809	$109.81	$109.80	$109.80
Purchase #7	$232.27	4.546%	$242.829	$242.83	$242.85	$242.80
7 purchase totals =	$1,163.73		$1,267.6267	$1,267.62	$1,267.60	$1,267.60