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	$74.92	4.280%	$78.1266	$78.13	$78.15	$78.10
Purchase #2	$11.76	5.434%	$12.399	$12.40	$12.40	$12.40
Purchase #3	$89.69	13.768%	$102.0385	$102.04	$102.05	$102.00
Purchase #4	$70.72	4.354%	$73.7991	$73.80	$73.80	$73.80
Purchase #5	$21.73	10.426%	$23.9956	$24.00	$24.00	$24.00
Purchase #6	$65.43	9.523%	$71.6609	$71.66	$71.65	$71.70
Purchase #7	$150.27	7.870%	$162.0962	$162.10	$162.10	$162.10
7 purchase totals =	$484.52		$524.1159	$524.13	$524.15	$524.10