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	$60.89	11.227%	$67.7261	$67.73	$67.75	$67.70
Purchase #2	$98.53	13.280%	$111.6148	$111.61	$111.60	$111.60
Purchase #3	$174.72	7.604%	$188.0057	$188.01	$188.00	$188.00
Purchase #4	$7.45	11.590%	$8.3135	$8.31	$8.30	$8.30
Purchase #5	$103.80	6.685%	$110.739	$110.74	$110.75	$110.70
Purchase #6	$172.47	3.500%	$178.5065	$178.51	$178.50	$178.50
Purchase #7	$116.81	3.475%	$120.8691	$120.87	$120.85	$120.90
7 purchase totals =	$734.67		$785.7747	$785.78	$785.75	$785.70