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	$62.82	10.685%	$69.5323	$69.53	$69.55	$69.50
Purchase #2	$125.66	12.443%	$141.2959	$141.30	$141.30	$141.30
Purchase #3	$233.72	7.182%	$250.5058	$250.51	$250.50	$250.50
Purchase #4	$235.88	11.465%	$262.9236	$262.92	$262.90	$262.90
Purchase #5	$190.56	6.677%	$203.2837	$203.28	$203.30	$203.30
Purchase #6	$154.32	9.135%	$168.4171	$168.42	$168.40	$168.40
Purchase #7	$106.44	6.721%	$113.5938	$113.59	$113.60	$113.60
7 purchase totals =	$1,109.40		$1,209.5522	$1,209.55	$1,209.55	$1,209.50