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	$234.41	10.335%	$258.6363	$258.64	$258.65	$258.60
Purchase #2	$250.69	6.687%	$267.4536	$267.45	$267.45	$267.50
Purchase #3	$184.81	3.801%	$191.8346	$191.83	$191.85	$191.80
Purchase #4	$84.25	11.140%	$93.6355	$93.64	$93.65	$93.60
Purchase #5	$87.28	8.743%	$94.9109	$94.91	$94.90	$94.90
Purchase #6	$86.85	9.293%	$94.921	$94.92	$94.90	$94.90
Purchase #7	$91.41	10.396%	$100.913	$100.91	$100.90	$100.90
7 purchase totals =	$1,019.70		$1,102.3049	$1,102.30	$1,102.30	$1,102.20