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	$200.49	5.530%	$211.5771	$211.58	$211.60	$211.60
Purchase #2	$80.36	3.156%	$82.8962	$82.90	$82.90	$82.90
Purchase #3	$245.31	11.165%	$272.6989	$272.70	$272.70	$272.70
Purchase #4	$113.43	4.241%	$118.2406	$118.24	$118.25	$118.20
Purchase #5	$7.88	12.641%	$8.8761	$8.88	$8.90	$8.90
Purchase #6	$141.96	7.290%	$152.3089	$152.31	$152.30	$152.30
Purchase #7	$127.86	11.616%	$142.7122	$142.71	$142.70	$142.70
7 purchase totals =	$917.29		$989.3100	$989.32	$989.35	$989.30