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	$63.71	7.343%	$68.3882	$68.39	$68.40	$68.40
Purchase #2	$171.41	9.304%	$187.358	$187.36	$187.35	$187.40
Purchase #3	$55.33	4.618%	$57.8851	$57.89	$57.90	$57.90
Purchase #4	$60.88	11.447%	$67.8489	$67.85	$67.85	$67.80
Purchase #5	$146.80	6.407%	$156.2055	$156.21	$156.20	$156.20
Purchase #6	$235.34	10.694%	$260.5073	$260.51	$260.50	$260.50
Purchase #7	$240.41	7.782%	$259.1187	$259.12	$259.10	$259.10
7 purchase totals =	$973.88		$1,057.3117	$1,057.33	$1,057.30	$1,057.30