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	$137.40	9.150%	$149.9721	$149.97	$149.95	$150.00
Purchase #2	$119.91	12.178%	$134.5126	$134.51	$134.50	$134.50
Purchase #3	$69.76	3.856%	$72.4499	$72.45	$72.45	$72.40
Purchase #4	$178.48	7.456%	$191.7875	$191.79	$191.80	$191.80
Purchase #5	$114.27	11.818%	$127.7744	$127.77	$127.75	$127.80
Purchase #6	$195.83	7.275%	$210.0766	$210.08	$210.10	$210.10
Purchase #7	$160.72	12.825%	$181.3323	$181.33	$181.35	$181.30
7 purchase totals =	$976.37		$1,067.9054	$1,067.90	$1,067.90	$1,067.90