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	$142.75	6.690%	$152.3	$152.30	$152.30	$152.30
Purchase #2	$159.59	13.104%	$180.5027	$180.50	$180.50	$180.50
Purchase #3	$168.96	7.867%	$182.2521	$182.25	$182.25	$182.30
Purchase #4	$142.85	7.292%	$153.2666	$153.27	$153.25	$153.30
Purchase #5	$210.54	8.667%	$228.7875	$228.79	$228.80	$228.80
Purchase #6	$128.53	11.777%	$143.667	$143.67	$143.65	$143.70
Purchase #7	$63.39	12.648%	$71.4076	$71.41	$71.40	$71.40
7 purchase totals =	$1,016.61		$1,112.1835	$1,112.19	$1,112.15	$1,112.30