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	$155.56	3.260%	$160.6313	$160.63	$160.65	$160.60
Purchase #2	$31.56	3.865%	$32.7798	$32.78	$32.80	$32.80
Purchase #3	$28.27	3.371%	$29.223	$29.22	$29.20	$29.20
Purchase #4	$173.33	12.259%	$194.5785	$194.58	$194.60	$194.60
Purchase #5	$165.41	4.496%	$172.8468	$172.85	$172.85	$172.80
Purchase #6	$178.86	6.285%	$190.1014	$190.10	$190.10	$190.10
Purchase #7	$10.86	6.338%	$11.5483	$11.55	$11.55	$11.50
7 purchase totals =	$743.85		$791.7091	$791.71	$791.75	$791.60