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	$88.45	9.524%	$96.874	$96.87	$96.85	$96.90
Purchase #2	$240.71	13.534%	$273.2877	$273.29	$273.30	$273.30
Purchase #3	$165.36	4.726%	$173.1749	$173.17	$173.15	$173.20
Purchase #4	$133.68	10.627%	$147.8862	$147.89	$147.90	$147.90
Purchase #5	$216.52	3.399%	$223.8795	$223.88	$223.90	$223.90
Purchase #6	$41.90	8.120%	$45.3023	$45.30	$45.30	$45.30
Purchase #7	$189.38	3.806%	$196.5878	$196.59	$196.60	$196.60
7 purchase totals =	$1,076.00		$1,156.9924	$1,156.99	$1,157.00	$1,157.10