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	$229.85	5.498%	$242.4872	$242.49	$242.50	$242.50
Purchase #2	$116.62	9.660%	$127.8855	$127.89	$127.90	$127.90
Purchase #3	$101.65	4.453%	$106.1765	$106.18	$106.20	$106.20
Purchase #4	$248.80	7.275%	$266.9002	$266.90	$266.90	$266.90
Purchase #5	$224.28	7.245%	$240.5291	$240.53	$240.55	$240.50
Purchase #6	$85.73	8.282%	$92.8302	$92.83	$92.85	$92.80
Purchase #7	$162.28	3.260%	$167.5703	$167.57	$167.55	$167.60
7 purchase totals =	$1,169.21		$1,244.3790	$1,244.39	$1,244.45	$1,244.40