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	$152.71	7.661%	$164.4091	$164.41	$164.40	$164.40
Purchase #2	$73.37	3.481%	$75.924	$75.92	$75.90	$75.90
Purchase #3	$156.79	4.748%	$164.2344	$164.23	$164.25	$164.20
Purchase #4	$158.61	7.278%	$170.1536	$170.15	$170.15	$170.20
Purchase #5	$42.91	4.257%	$44.7367	$44.74	$44.75	$44.70
Purchase #6	$174.90	4.320%	$182.4557	$182.46	$182.45	$182.50
Purchase #7	$83.53	8.312%	$90.473	$90.47	$90.45	$90.50
7 purchase totals =	$842.82		$892.3865	$892.38	$892.35	$892.40