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	$220.59	7.441%	$237.0041	$237.00	$237.00	$237.00
Purchase #2	$78.50	13.531%	$89.1218	$89.12	$89.10	$89.10
Purchase #3	$92.70	11.297%	$103.1723	$103.17	$103.15	$103.20
Purchase #4	$98.76	12.821%	$111.422	$111.42	$111.40	$111.40
Purchase #5	$110.33	11.590%	$123.1172	$123.12	$123.10	$123.10
Purchase #6	$102.99	3.285%	$106.3732	$106.37	$106.35	$106.40
Purchase #7	$246.47	4.383%	$257.2728	$257.27	$257.25	$257.30
7 purchase totals =	$950.34		$1,027.4834	$1,027.47	$1,027.35	$1,027.50