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	$142.89	7.772%	$153.9954	$154.00	$154.00	$154.00
Purchase #2	$147.39	4.279%	$153.6968	$153.70	$153.70	$153.70
Purchase #3	$100.43	12.437%	$112.9205	$112.92	$112.90	$112.90
Purchase #4	$126.57	10.642%	$140.0396	$140.04	$140.05	$140.00
Purchase #5	$174.57	4.790%	$182.9319	$182.93	$182.95	$182.90
Purchase #6	$242.48	6.194%	$257.4992	$257.50	$257.50	$257.50
Purchase #7	$82.90	7.564%	$89.1706	$89.17	$89.15	$89.20
7 purchase totals =	$1,017.23		$1,090.2540	$1,090.26	$1,090.25	$1,090.20