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	$214.88	6.687%	$229.249	$229.25	$229.25	$229.20
Purchase #2	$125.70	4.853%	$131.8002	$131.80	$131.80	$131.80
Purchase #3	$232.98	9.857%	$255.9448	$255.94	$255.95	$255.90
Purchase #4	$94.28	3.444%	$97.527	$97.53	$97.55	$97.50
Purchase #5	$220.87	12.588%	$248.6731	$248.67	$248.65	$248.70
Purchase #6	$169.27	6.857%	$180.8768	$180.88	$180.90	$180.90
Purchase #7	$73.33	7.336%	$78.7095	$78.71	$78.70	$78.70
7 purchase totals =	$1,131.31		$1,222.7804	$1,222.78	$1,222.80	$1,222.70