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	$215.54	12.529%	$242.545	$242.55	$242.55	$242.50
Purchase #2	$225.81	12.745%	$254.5895	$254.59	$254.60	$254.60
Purchase #3	$74.95	3.114%	$77.2839	$77.28	$77.30	$77.30
Purchase #4	$223.69	4.522%	$233.8053	$233.81	$233.80	$233.80
Purchase #5	$210.88	10.622%	$233.2797	$233.28	$233.30	$233.30
Purchase #6	$242.71	10.761%	$268.828	$268.83	$268.85	$268.80
Purchase #7	$139.83	10.552%	$154.5849	$154.58	$154.60	$154.60
7 purchase totals =	$1,333.41		$1,464.9163	$1,464.92	$1,465.00	$1,464.90