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	$214.72	3.721%	$222.7097	$222.71	$222.70	$222.70
Purchase #2	$67.80	6.217%	$72.0151	$72.02	$72.00	$72.00
Purchase #3	$245.85	7.179%	$263.4996	$263.50	$263.50	$263.50
Purchase #4	$229.58	3.865%	$238.4533	$238.45	$238.45	$238.50
Purchase #5	$244.78	7.107%	$262.1765	$262.18	$262.20	$262.20
Purchase #6	$35.63	4.353%	$37.181	$37.18	$37.20	$37.20
Purchase #7	$28.53	4.697%	$29.8701	$29.87	$29.85	$29.90
7 purchase totals =	$1,066.89		$1,125.9053	$1,125.91	$1,125.90	$1,126.00