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	$249.54	4.682%	$261.2235	$261.22	$261.20	$261.20
Purchase #2	$38.54	13.803%	$43.8597	$43.86	$43.85	$43.90
Purchase #3	$147.41	4.225%	$153.6381	$153.64	$153.65	$153.60
Purchase #4	$57.51	7.172%	$61.6346	$61.63	$61.65	$61.60
Purchase #5	$130.42	9.580%	$142.9142	$142.91	$142.90	$142.90
Purchase #6	$128.26	11.276%	$142.7226	$142.72	$142.70	$142.70
Purchase #7	$245.43	9.475%	$268.6845	$268.68	$268.70	$268.70
7 purchase totals =	$997.11		$1,074.6772	$1,074.66	$1,074.65	$1,074.60