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	$73.86	5.681%	$78.056	$78.06	$78.05	$78.10
Purchase #2	$73.65	7.355%	$79.067	$79.07	$79.05	$79.10
Purchase #3	$18.45	9.810%	$20.2599	$20.26	$20.25	$20.30
Purchase #4	$137.69	12.138%	$154.4028	$154.40	$154.40	$154.40
Purchase #5	$98.92	4.606%	$103.4763	$103.48	$103.50	$103.50
Purchase #6	$88.60	4.527%	$92.6109	$92.61	$92.60	$92.60
Purchase #7	$45.36	8.725%	$49.3177	$49.32	$49.30	$49.30
7 purchase totals =	$536.53		$577.1906	$577.20	$577.15	$577.30