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	$65.44	11.147%	$72.7346	$72.73	$72.75	$72.70
Purchase #2	$109.65	3.306%	$113.275	$113.28	$113.30	$113.30
Purchase #3	$37.85	6.365%	$40.2592	$40.26	$40.25	$40.30
Purchase #4	$165.37	5.517%	$174.4935	$174.49	$174.50	$174.50
Purchase #5	$79.28	9.314%	$86.6641	$86.66	$86.65	$86.70
Purchase #6	$244.27	7.813%	$263.3548	$263.35	$263.35	$263.40
Purchase #7	$27.47	7.813%	$29.6162	$29.62	$29.60	$29.60
7 purchase totals =	$729.33		$780.3974	$780.39	$780.40	$780.50