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	$62.64	8.194%	$67.7727	$67.77	$67.75	$67.80
Purchase #2	$104.40	8.437%	$113.2082	$113.21	$113.20	$113.20
Purchase #3	$100.85	3.251%	$104.1286	$104.13	$104.15	$104.10
Purchase #4	$38.34	5.373%	$40.4	$40.40	$40.40	$40.40
Purchase #5	$88.90	13.346%	$100.7646	$100.76	$100.75	$100.80
Purchase #6	$224.97	4.689%	$235.5188	$235.52	$235.50	$235.50
Purchase #7	$86.41	11.558%	$96.3973	$96.40	$96.40	$96.40
7 purchase totals =	$706.51		$758.1902	$758.19	$758.15	$758.20