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	$185.29	6.165%	$196.7131	$196.71	$196.70	$196.70
Purchase #2	$226.32	8.360%	$245.2404	$245.24	$245.25	$245.20
Purchase #3	$117.80	4.632%	$123.2565	$123.26	$123.25	$123.30
Purchase #4	$29.36	11.361%	$32.6956	$32.70	$32.70	$32.70
Purchase #5	$159.81	12.486%	$179.7639	$179.76	$179.75	$179.80
Purchase #6	$85.82	10.171%	$94.5488	$94.55	$94.55	$94.50
Purchase #7	$241.89	12.146%	$271.27	$271.27	$271.25	$271.30
7 purchase totals =	$1,046.29		$1,143.4883	$1,143.49	$1,143.45	$1,143.50