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	$149.73	10.147%	$164.9231	$164.92	$164.90	$164.90
Purchase #2	$70.88	3.850%	$73.6089	$73.61	$73.60	$73.60
Purchase #3	$231.74	3.867%	$240.7014	$240.70	$240.70	$240.70
Purchase #4	$242.77	3.269%	$250.7062	$250.71	$250.70	$250.70
Purchase #5	$164.91	11.528%	$183.9208	$183.92	$183.90	$183.90
Purchase #6	$85.32	6.180%	$90.5928	$90.59	$90.60	$90.60
Purchase #7	$198.44	10.447%	$219.171	$219.17	$219.15	$219.20
7 purchase totals =	$1,143.79		$1,223.6242	$1,223.62	$1,223.55	$1,223.60