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	$218.30	3.679%	$226.3313	$226.33	$226.35	$226.30
Purchase #2	$223.96	11.449%	$249.6012	$249.60	$249.60	$249.60
Purchase #3	$168.52	3.399%	$174.248	$174.25	$174.25	$174.20
Purchase #4	$24.87	12.384%	$27.9499	$27.95	$27.95	$27.90
Purchase #5	$89.91	5.786%	$95.1122	$95.11	$95.10	$95.10
Purchase #6	$37.98	6.394%	$40.4084	$40.41	$40.40	$40.40
Purchase #7	$249.82	13.138%	$282.6414	$282.64	$282.65	$282.60
7 purchase totals =	$1,013.36		$1,096.2924	$1,096.29	$1,096.30	$1,096.10