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	$17.49	8.537%	$18.9831	$18.98	$19.00	$19.00
Purchase #2	$83.69	7.816%	$90.2312	$90.23	$90.25	$90.20
Purchase #3	$218.53	5.794%	$231.1916	$231.19	$231.20	$231.20
Purchase #4	$169.31	6.144%	$179.7124	$179.71	$179.70	$179.70
Purchase #5	$135.94	11.581%	$151.6832	$151.68	$151.70	$151.70
Purchase #6	$95.43	3.501%	$98.771	$98.77	$98.75	$98.80
Purchase #7	$228.38	8.268%	$247.2625	$247.26	$247.25	$247.30
7 purchase totals =	$948.77		$1,017.8350	$1,017.82	$1,017.85	$1,017.90