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	$68.96	10.351%	$76.098	$76.10	$76.10	$76.10
Purchase #2	$219.99	13.832%	$250.419	$250.42	$250.40	$250.40
Purchase #3	$178.46	12.609%	$200.962	$200.96	$200.95	$201.00
Purchase #4	$97.84	12.305%	$109.8792	$109.88	$109.90	$109.90
Purchase #5	$53.37	9.388%	$58.3804	$58.38	$58.40	$58.40
Purchase #6	$125.62	13.801%	$142.9568	$142.96	$142.95	$143.00
Purchase #7	$90.53	9.536%	$99.1629	$99.16	$99.15	$99.20
7 purchase totals =	$834.77		$937.8583	$937.86	$937.85	$938.00