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	$228.40	12.484%	$256.9135	$256.91	$256.90	$256.90
Purchase #2	$177.38	4.455%	$185.2823	$185.28	$185.30	$185.30
Purchase #3	$215.36	3.431%	$222.749	$222.75	$222.75	$222.70
Purchase #4	$207.79	8.374%	$225.1903	$225.19	$225.20	$225.20
Purchase #5	$165.89	3.259%	$171.2964	$171.30	$171.30	$171.30
Purchase #6	$88.44	11.183%	$98.3302	$98.33	$98.35	$98.30
Purchase #7	$90.82	9.285%	$99.2526	$99.25	$99.25	$99.30
7 purchase totals =	$1,174.08		$1,259.0143	$1,259.01	$1,259.05	$1,259.00