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	$241.34	11.416%	$268.8914	$268.89	$268.90	$268.90
Purchase #2	$92.83	5.499%	$97.9347	$97.93	$97.95	$97.90
Purchase #3	$46.64	8.789%	$50.7392	$50.74	$50.75	$50.70
Purchase #4	$171.42	5.506%	$180.8584	$180.86	$180.85	$180.90
Purchase #5	$61.66	8.860%	$67.1231	$67.12	$67.10	$67.10
Purchase #6	$170.31	7.800%	$183.5942	$183.59	$183.60	$183.60
Purchase #7	$196.74	8.188%	$212.8491	$212.85	$212.85	$212.80
7 purchase totals =	$980.94		$1,061.9901	$1,061.98	$1,062.00	$1,061.90