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	$153.26	13.790%	$174.3946	$174.39	$174.40	$174.40
Purchase #2	$35.38	12.799%	$39.9083	$39.91	$39.90	$39.90
Purchase #3	$218.37	10.483%	$241.2617	$241.26	$241.25	$241.30
Purchase #4	$46.56	9.601%	$51.0302	$51.03	$51.05	$51.00
Purchase #5	$58.73	13.852%	$66.8653	$66.87	$66.85	$66.90
Purchase #6	$130.71	8.847%	$142.2739	$142.27	$142.25	$142.30
Purchase #7	$178.33	4.219%	$185.8537	$185.85	$185.85	$185.90
7 purchase totals =	$821.34		$901.5877	$901.58	$901.55	$901.70