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	$107.90	3.245%	$111.4014	$111.40	$111.40	$111.40
Purchase #2	$122.98	3.657%	$127.4774	$127.48	$127.50	$127.50
Purchase #3	$155.56	9.437%	$170.2402	$170.24	$170.25	$170.20
Purchase #4	$148.27	9.548%	$162.4268	$162.43	$162.45	$162.40
Purchase #5	$144.28	8.353%	$156.3317	$156.33	$156.35	$156.30
Purchase #6	$95.44	3.540%	$98.8186	$98.82	$98.80	$98.80
Purchase #7	$23.59	7.171%	$25.2816	$25.28	$25.30	$25.30
7 purchase totals =	$798.02		$851.9777	$851.98	$852.05	$851.90