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	$164.59	11.372%	$183.3072	$183.31	$183.30	$183.30
Purchase #2	$191.57	13.447%	$217.3304	$217.33	$217.35	$217.30
Purchase #3	$73.99	5.684%	$78.1956	$78.20	$78.20	$78.20
Purchase #4	$91.64	8.378%	$99.3176	$99.32	$99.30	$99.30
Purchase #5	$213.80	12.386%	$240.2813	$240.28	$240.30	$240.30
Purchase #6	$149.75	13.227%	$169.5574	$169.56	$169.55	$169.60
Purchase #7	$171.50	4.516%	$179.2449	$179.24	$179.25	$179.20
7 purchase totals =	$1,056.84		$1,167.2344	$1,167.24	$1,167.25	$1,167.20