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	$127.60	4.316%	$133.1072	$133.11	$133.10	$133.10
Purchase #2	$30.31	8.642%	$32.9294	$32.93	$32.95	$32.90
Purchase #3	$241.83	11.636%	$269.9693	$269.97	$269.95	$270.00
Purchase #4	$90.35	6.236%	$95.9842	$95.98	$96.00	$96.00
Purchase #5	$30.75	3.674%	$31.8798	$31.88	$31.90	$31.90
Purchase #6	$90.45	8.817%	$98.425	$98.43	$98.45	$98.40
Purchase #7	$66.35	7.368%	$71.2387	$71.24	$71.25	$71.20
7 purchase totals =	$677.64		$733.5336	$733.54	$733.60	$733.50