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	$92.69	8.689%	$100.7438	$100.74	$100.75	$100.70
Purchase #2	$144.59	4.154%	$150.5963	$150.60	$150.60	$150.60
Purchase #3	$116.59	5.747%	$123.2904	$123.29	$123.30	$123.30
Purchase #4	$190.67	7.656%	$205.2677	$205.27	$205.25	$205.30
Purchase #5	$125.37	3.670%	$129.9711	$129.97	$129.95	$130.00
Purchase #6	$55.72	4.573%	$58.2681	$58.27	$58.25	$58.30
Purchase #7	$88.98	8.596%	$96.6287	$96.63	$96.65	$96.60
7 purchase totals =	$814.61		$864.7661	$864.77	$864.75	$864.80