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	$35.44	5.338%	$37.3318	$37.33	$37.35	$37.30
Purchase #2	$64.31	13.381%	$72.9153	$72.92	$72.90	$72.90
Purchase #3	$91.60	3.250%	$94.577	$94.58	$94.60	$94.60
Purchase #4	$211.87	9.136%	$231.2264	$231.23	$231.25	$231.20
Purchase #5	$182.52	4.692%	$191.0838	$191.08	$191.10	$191.10
Purchase #6	$19.55	4.751%	$20.4788	$20.48	$20.50	$20.50
Purchase #7	$222.45	6.368%	$236.6156	$236.62	$236.60	$236.60
7 purchase totals =	$827.74		$884.2287	$884.24	$884.30	$884.20