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	$8.67	3.258%	$8.9525	$8.95	$8.95	$9.00
Purchase #2	$233.91	7.209%	$250.7726	$250.77	$250.75	$250.80
Purchase #3	$185.71	6.798%	$198.3346	$198.33	$198.35	$198.30
Purchase #4	$29.33	12.436%	$32.9775	$32.98	$33.00	$33.00
Purchase #5	$28.76	6.449%	$30.6147	$30.61	$30.60	$30.60
Purchase #6	$111.67	13.844%	$127.1296	$127.13	$127.15	$127.10
Purchase #7	$56.60	5.869%	$59.9219	$59.92	$59.90	$59.90
7 purchase totals =	$654.65		$708.7034	$708.69	$708.70	$708.70