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	$222.59	9.728%	$244.2436	$244.24	$244.25	$244.20
Purchase #2	$6.74	7.615%	$7.2533	$7.25	$7.25	$7.30
Purchase #3	$132.70	3.600%	$137.4772	$137.48	$137.50	$137.50
Purchase #4	$73.73	13.850%	$83.9416	$83.94	$83.95	$83.90
Purchase #5	$221.33	3.827%	$229.8003	$229.80	$229.80	$229.80
Purchase #6	$134.96	5.663%	$142.6028	$142.60	$142.60	$142.60
Purchase #7	$202.55	3.603%	$209.8479	$209.85	$209.85	$209.80
7 purchase totals =	$994.60		$1,055.1667	$1,055.16	$1,055.20	$1,055.10