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	$45.25	3.443%	$46.808	$46.81	$46.80	$46.80
Purchase #2	$164.73	12.591%	$185.4712	$185.47	$185.45	$185.50
Purchase #3	$216.95	3.607%	$224.7754	$224.78	$224.80	$224.80
Purchase #4	$57.87	3.288%	$59.7728	$59.77	$59.75	$59.80
Purchase #5	$216.87	12.266%	$243.4713	$243.47	$243.45	$243.50
Purchase #6	$192.50	9.598%	$210.9762	$210.98	$211.00	$211.00
Purchase #7	$84.51	5.744%	$89.3643	$89.36	$89.35	$89.40
7 purchase totals =	$978.68		$1,060.6392	$1,060.64	$1,060.60	$1,060.80