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	$86.71	13.651%	$98.5468	$98.55	$98.55	$98.50
Purchase #2	$132.86	13.456%	$150.7376	$150.74	$150.75	$150.70
Purchase #3	$74.42	11.667%	$83.1026	$83.10	$83.10	$83.10
Purchase #4	$48.83	7.576%	$52.5294	$52.53	$52.55	$52.50
Purchase #5	$105.76	12.551%	$119.0339	$119.03	$119.05	$119.00
Purchase #6	$165.52	11.776%	$185.0116	$185.01	$185.00	$185.00
Purchase #7	$243.75	7.274%	$261.4804	$261.48	$261.50	$261.50
7 purchase totals =	$857.85		$950.4423	$950.44	$950.50	$950.30