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	$68.79	6.242%	$73.0839	$73.08	$73.10	$73.10
Purchase #2	$188.26	4.162%	$196.0954	$196.10	$196.10	$196.10
Purchase #3	$99.63	3.198%	$102.8162	$102.82	$102.80	$102.80
Purchase #4	$249.56	13.665%	$283.6624	$283.66	$283.65	$283.70
Purchase #5	$197.33	12.775%	$222.5389	$222.54	$222.55	$222.50
Purchase #6	$64.89	3.720%	$67.3039	$67.30	$67.30	$67.30
Purchase #7	$248.72	5.759%	$263.0438	$263.04	$263.05	$263.00
7 purchase totals =	$1,117.18		$1,208.5445	$1,208.54	$1,208.55	$1,208.50