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	$83.84	10.263%	$92.4445	$92.44	$92.45	$92.40
Purchase #2	$229.65	3.147%	$236.8771	$236.88	$236.90	$236.90
Purchase #3	$222.40	12.579%	$250.3757	$250.38	$250.40	$250.40
Purchase #4	$142.92	7.664%	$153.8734	$153.87	$153.85	$153.90
Purchase #5	$72.74	12.578%	$81.8892	$81.89	$81.90	$81.90
Purchase #6	$232.42	5.622%	$245.4867	$245.49	$245.50	$245.50
Purchase #7	$46.56	9.260%	$50.8715	$50.87	$50.85	$50.90
7 purchase totals =	$1,030.53		$1,111.8181	$1,111.82	$1,111.85	$1,111.90