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	$127.27	11.736%	$142.2064	$142.21	$142.20	$142.20
Purchase #2	$42.83	9.291%	$46.8093	$46.81	$46.80	$46.80
Purchase #3	$80.84	5.434%	$85.2328	$85.23	$85.25	$85.20
Purchase #4	$196.93	6.774%	$210.27	$210.27	$210.25	$210.30
Purchase #5	$35.96	8.454%	$39.0001	$39.00	$39.00	$39.00
Purchase #6	$181.56	3.843%	$188.5374	$188.54	$188.55	$188.50
Purchase #7	$24.25	8.844%	$26.3947	$26.39	$26.40	$26.40
7 purchase totals =	$689.64		$738.4507	$738.45	$738.45	$738.40