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	$152.25	5.255%	$160.2507	$160.25	$160.25	$160.30
Purchase #2	$151.39	12.645%	$170.5333	$170.53	$170.55	$170.50
Purchase #3	$91.89	6.845%	$98.1799	$98.18	$98.20	$98.20
Purchase #4	$167.80	12.112%	$188.1239	$188.12	$188.10	$188.10
Purchase #5	$54.72	5.602%	$57.7854	$57.79	$57.80	$57.80
Purchase #6	$161.60	6.492%	$172.0911	$172.09	$172.10	$172.10
Purchase #7	$183.89	3.514%	$190.3519	$190.35	$190.35	$190.40
7 purchase totals =	$963.54		$1,037.3162	$1,037.31	$1,037.35	$1,037.40