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	$176.93	4.714%	$185.2705	$185.27	$185.25	$185.30
Purchase #2	$80.40	4.357%	$83.903	$83.90	$83.90	$83.90
Purchase #3	$93.67	6.525%	$99.782	$99.78	$99.80	$99.80
Purchase #4	$10.96	4.109%	$11.4103	$11.41	$11.40	$11.40
Purchase #5	$118.92	6.723%	$126.915	$126.92	$126.90	$126.90
Purchase #6	$127.86	12.463%	$143.7952	$143.80	$143.80	$143.80
Purchase #7	$172.34	7.464%	$185.2035	$185.20	$185.20	$185.20
7 purchase totals =	$781.08		$836.2795	$836.28	$836.25	$836.30