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	$201.92	13.286%	$228.7471	$228.75	$228.75	$228.70
Purchase #2	$199.89	12.694%	$225.264	$225.26	$225.25	$225.30
Purchase #3	$196.40	12.207%	$220.3745	$220.37	$220.35	$220.40
Purchase #4	$109.35	6.266%	$116.2019	$116.20	$116.20	$116.20
Purchase #5	$185.69	5.799%	$196.4582	$196.46	$196.45	$196.50
Purchase #6	$84.61	5.557%	$89.3118	$89.31	$89.30	$89.30
Purchase #7	$127.80	11.472%	$142.4612	$142.46	$142.45	$142.50
7 purchase totals =	$1,105.66		$1,218.8187	$1,218.81	$1,218.75	$1,218.90