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	$168.32	13.405%	$190.8833	$190.88	$190.90	$190.90
Purchase #2	$29.76	12.611%	$33.513	$33.51	$33.50	$33.50
Purchase #3	$104.45	13.286%	$118.3272	$118.33	$118.35	$118.30
Purchase #4	$83.86	6.402%	$89.2287	$89.23	$89.25	$89.20
Purchase #5	$44.80	11.780%	$50.0774	$50.08	$50.10	$50.10
Purchase #6	$67.88	3.387%	$70.1791	$70.18	$70.20	$70.20
Purchase #7	$188.27	10.360%	$207.7748	$207.77	$207.75	$207.80
7 purchase totals =	$687.34		$759.9835	$759.98	$760.05	$760.00