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	$142.35	13.868%	$162.0911	$162.09	$162.10	$162.10
Purchase #2	$58.95	5.817%	$62.3791	$62.38	$62.40	$62.40
Purchase #3	$169.53	3.293%	$175.1126	$175.11	$175.10	$175.10
Purchase #4	$245.53	5.700%	$259.5252	$259.53	$259.55	$259.50
Purchase #5	$91.59	8.605%	$99.4713	$99.47	$99.45	$99.50
Purchase #6	$127.96	3.199%	$132.0534	$132.05	$132.05	$132.10
Purchase #7	$148.83	11.201%	$165.5004	$165.50	$165.50	$165.50
7 purchase totals =	$984.74		$1,056.1331	$1,056.13	$1,056.15	$1,056.20