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	$77.86	11.476%	$86.7952	$86.80	$86.80	$86.80
Purchase #2	$81.26	13.652%	$92.3536	$92.35	$92.35	$92.40
Purchase #3	$141.29	13.727%	$160.6849	$160.68	$160.70	$160.70
Purchase #4	$134.92	4.168%	$140.5435	$140.54	$140.55	$140.50
Purchase #5	$139.35	12.131%	$156.2545	$156.25	$156.25	$156.30
Purchase #6	$43.28	4.274%	$45.1298	$45.13	$45.15	$45.10
Purchase #7	$58.86	4.589%	$61.5611	$61.56	$61.55	$61.60
7 purchase totals =	$676.82		$743.3226	$743.31	$743.35	$743.40