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	$169.26	11.333%	$188.4422	$188.44	$188.45	$188.40
Purchase #2	$74.82	6.335%	$79.5598	$79.56	$79.55	$79.60
Purchase #3	$167.46	10.620%	$185.2443	$185.24	$185.25	$185.20
Purchase #4	$212.89	3.705%	$220.7776	$220.78	$220.80	$220.80
Purchase #5	$54.92	13.458%	$62.3111	$62.31	$62.30	$62.30
Purchase #6	$130.56	6.784%	$139.4172	$139.42	$139.40	$139.40
Purchase #7	$88.30	11.540%	$98.4898	$98.49	$98.50	$98.50
7 purchase totals =	$898.21		$974.2420	$974.24	$974.25	$974.20