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	$189.98	7.386%	$204.0119	$204.01	$204.00	$204.00
Purchase #2	$78.64	13.621%	$89.3516	$89.35	$89.35	$89.40
Purchase #3	$59.82	7.444%	$64.273	$64.27	$64.25	$64.30
Purchase #4	$227.65	12.146%	$255.3004	$255.30	$255.30	$255.30
Purchase #5	$33.73	7.709%	$36.3302	$36.33	$36.35	$36.30
Purchase #6	$122.85	11.161%	$136.5613	$136.56	$136.55	$136.60
Purchase #7	$223.83	6.352%	$238.0477	$238.05	$238.05	$238.00
7 purchase totals =	$936.50		$1,023.8761	$1,023.87	$1,023.85	$1,023.90