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	$87.33	8.166%	$94.4614	$94.46	$94.45	$94.50
Purchase #2	$148.62	4.818%	$155.7805	$155.78	$155.80	$155.80
Purchase #3	$176.33	11.332%	$196.3117	$196.31	$196.30	$196.30
Purchase #4	$213.97	6.710%	$228.3274	$228.33	$228.35	$228.30
Purchase #5	$79.78	7.644%	$85.8784	$85.88	$85.90	$85.90
Purchase #6	$118.90	9.434%	$130.117	$130.12	$130.10	$130.10
Purchase #7	$194.44	13.713%	$221.1036	$221.10	$221.10	$221.10
7 purchase totals =	$1,019.37		$1,111.9800	$1,111.98	$1,112.00	$1,112.00