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	$168.85	11.518%	$188.2981	$188.30	$188.30	$188.30
Purchase #2	$181.50	9.348%	$198.4666	$198.47	$198.45	$198.50
Purchase #3	$196.25	11.330%	$218.4851	$218.49	$218.50	$218.50
Purchase #4	$179.49	11.780%	$200.6339	$200.63	$200.65	$200.60
Purchase #5	$247.28	9.253%	$270.1608	$270.16	$270.15	$270.20
Purchase #6	$100.28	9.207%	$109.5128	$109.51	$109.50	$109.50
Purchase #7	$43.56	8.795%	$47.3911	$47.39	$47.40	$47.40
7 purchase totals =	$1,117.21		$1,232.9484	$1,232.95	$1,232.95	$1,233.00