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	$88.99	10.820%	$98.6187	$98.62	$98.60	$98.60
Purchase #2	$230.98	12.544%	$259.9541	$259.95	$259.95	$260.00
Purchase #3	$176.38	7.661%	$189.8925	$189.89	$189.90	$189.90
Purchase #4	$243.68	10.285%	$268.7425	$268.74	$268.75	$268.70
Purchase #5	$70.40	11.494%	$78.4918	$78.49	$78.50	$78.50
Purchase #6	$75.45	3.253%	$77.9044	$77.90	$77.90	$77.90
Purchase #7	$91.67	8.293%	$99.2722	$99.27	$99.25	$99.30
7 purchase totals =	$977.55		$1,072.8762	$1,072.86	$1,072.85	$1,072.90