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	$156.57	10.320%	$172.728	$172.73	$172.75	$172.70
Purchase #2	$33.80	9.751%	$37.0958	$37.10	$37.10	$37.10
Purchase #3	$140.96	8.718%	$153.2489	$153.25	$153.25	$153.20
Purchase #4	$76.85	7.172%	$82.3617	$82.36	$82.35	$82.40
Purchase #5	$218.28	4.483%	$228.0655	$228.07	$228.05	$228.10
Purchase #6	$52.28	8.391%	$56.6668	$56.67	$56.65	$56.70
Purchase #7	$81.93	13.223%	$92.7636	$92.76	$92.75	$92.80
7 purchase totals =	$760.67		$822.9303	$822.94	$822.90	$823.00