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	$225.67	5.145%	$237.2807	$237.28	$237.30	$237.30
Purchase #2	$107.64	9.666%	$118.0445	$118.04	$118.05	$118.00
Purchase #3	$99.52	4.285%	$103.7844	$103.78	$103.80	$103.80
Purchase #4	$55.88	11.297%	$62.1928	$62.19	$62.20	$62.20
Purchase #5	$28.39	11.279%	$31.5921	$31.59	$31.60	$31.60
Purchase #6	$63.50	12.514%	$71.4464	$71.45	$71.45	$71.40
Purchase #7	$70.68	10.324%	$77.977	$77.98	$78.00	$78.00
7 purchase totals =	$651.28		$702.3179	$702.31	$702.40	$702.30