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	$196.90	11.222%	$218.9961	$219.00	$219.00	$219.00
Purchase #2	$54.72	4.313%	$57.0801	$57.08	$57.10	$57.10
Purchase #3	$88.50	4.410%	$92.4029	$92.40	$92.40	$92.40
Purchase #4	$103.81	6.747%	$110.8141	$110.81	$110.80	$110.80
Purchase #5	$55.90	6.365%	$59.458	$59.46	$59.45	$59.50
Purchase #6	$89.40	10.735%	$98.9971	$99.00	$99.00	$99.00
Purchase #7	$188.83	10.150%	$207.9962	$208.00	$208.00	$208.00
7 purchase totals =	$778.06		$845.7445	$845.75	$845.75	$845.80