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	$74.33	5.232%	$78.2189	$78.22	$78.20	$78.20
Purchase #2	$100.79	10.853%	$111.7287	$111.73	$111.75	$111.70
Purchase #3	$237.79	12.838%	$268.3175	$268.32	$268.30	$268.30
Purchase #4	$6.40	13.514%	$7.2649	$7.26	$7.25	$7.30
Purchase #5	$117.83	10.497%	$130.1986	$130.20	$130.20	$130.20
Purchase #6	$215.67	9.358%	$235.8524	$235.85	$235.85	$235.90
Purchase #7	$232.72	13.382%	$263.8626	$263.86	$263.85	$263.90
7 purchase totals =	$985.53		$1,095.4436	$1,095.44	$1,095.40	$1,095.50