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	$213.36	7.522%	$229.4089	$229.41	$229.40	$229.40
Purchase #2	$73.36	12.220%	$82.3246	$82.32	$82.30	$82.30
Purchase #3	$248.97	5.300%	$262.1654	$262.17	$262.15	$262.20
Purchase #4	$32.39	4.245%	$33.765	$33.77	$33.75	$33.80
Purchase #5	$223.95	13.336%	$253.816	$253.82	$253.80	$253.80
Purchase #6	$70.53	3.257%	$72.8272	$72.83	$72.85	$72.80
Purchase #7	$202.46	4.715%	$212.006	$212.01	$212.00	$212.00
7 purchase totals =	$1,065.02		$1,146.3131	$1,146.33	$1,146.25	$1,146.30