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	$82.71	11.777%	$92.4508	$92.45	$92.45	$92.50
Purchase #2	$56.68	10.269%	$62.5005	$62.50	$62.50	$62.50
Purchase #3	$43.33	4.225%	$45.1607	$45.16	$45.15	$45.20
Purchase #4	$161.32	8.110%	$174.4031	$174.40	$174.40	$174.40
Purchase #5	$233.56	4.179%	$243.3205	$243.32	$243.30	$243.30
Purchase #6	$106.77	13.820%	$121.5256	$121.53	$121.55	$121.50
Purchase #7	$41.49	4.615%	$43.4048	$43.40	$43.40	$43.40
7 purchase totals =	$725.86		$782.7660	$782.76	$782.75	$782.80