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	$53.64	10.552%	$59.3001	$59.30	$59.30	$59.30
Purchase #2	$234.57	7.825%	$252.9251	$252.93	$252.95	$252.90
Purchase #3	$169.26	9.681%	$185.6461	$185.65	$185.65	$185.60
Purchase #4	$250.34	7.405%	$268.8777	$268.88	$268.90	$268.90
Purchase #5	$112.25	10.108%	$123.5962	$123.60	$123.60	$123.60
Purchase #6	$81.36	6.353%	$86.5288	$86.53	$86.55	$86.50
Purchase #7	$157.88	6.468%	$168.0917	$168.09	$168.10	$168.10
7 purchase totals =	$1,059.30		$1,144.9657	$1,144.98	$1,145.05	$1,144.90