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	$67.60	9.499%	$74.0213	$74.02	$74.00	$74.00
Purchase #2	$89.39	12.129%	$100.2321	$100.23	$100.25	$100.20
Purchase #3	$65.81	10.203%	$72.5246	$72.52	$72.50	$72.50
Purchase #4	$194.35	10.755%	$215.2523	$215.25	$215.25	$215.30
Purchase #5	$102.80	11.672%	$114.7988	$114.80	$114.80	$114.80
Purchase #6	$58.25	8.219%	$63.0376	$63.04	$63.05	$63.00
Purchase #7	$130.52	8.848%	$142.0684	$142.07	$142.05	$142.10
7 purchase totals =	$708.72		$781.9351	$781.93	$781.90	$781.90