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	$180.53	5.321%	$190.136	$190.14	$190.15	$190.10
Purchase #2	$181.62	3.662%	$188.2709	$188.27	$188.25	$188.30
Purchase #3	$9.56	8.182%	$10.3422	$10.34	$10.35	$10.30
Purchase #4	$130.61	8.309%	$141.4624	$141.46	$141.45	$141.50
Purchase #5	$54.82	8.681%	$59.5789	$59.58	$59.60	$59.60
Purchase #6	$147.93	4.477%	$154.5528	$154.55	$154.55	$154.60
Purchase #7	$52.66	6.399%	$56.0297	$56.03	$56.05	$56.00
7 purchase totals =	$757.73		$800.3729	$800.37	$800.40	$800.40