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	$43.49	7.170%	$46.6082	$46.61	$46.60	$46.60
Purchase #2	$95.69	7.691%	$103.0495	$103.05	$103.05	$103.00
Purchase #3	$146.84	13.152%	$166.1524	$166.15	$166.15	$166.20
Purchase #4	$55.60	13.831%	$63.29	$63.29	$63.30	$63.30
Purchase #5	$51.32	7.306%	$55.0694	$55.07	$55.05	$55.10
Purchase #6	$82.41	4.498%	$86.1168	$86.12	$86.10	$86.10
Purchase #7	$124.27	12.112%	$139.3216	$139.32	$139.30	$139.30
7 purchase totals =	$599.62		$659.6079	$659.61	$659.55	$659.60