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	$243.46	7.686%	$262.1723	$262.17	$262.15	$262.20
Purchase #2	$110.53	11.661%	$123.4189	$123.42	$123.40	$123.40
Purchase #3	$41.91	3.321%	$43.3018	$43.30	$43.30	$43.30
Purchase #4	$207.31	3.759%	$215.1028	$215.10	$215.10	$215.10
Purchase #5	$245.60	3.444%	$254.0585	$254.06	$254.05	$254.10
Purchase #6	$86.62	4.283%	$90.3299	$90.33	$90.35	$90.30
Purchase #7	$150.78	12.302%	$169.329	$169.33	$169.35	$169.30
7 purchase totals =	$1,086.21		$1,157.7132	$1,157.71	$1,157.70	$1,157.70