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	$98.92	6.111%	$104.965	$104.97	$104.95	$105.00
Purchase #2	$85.87	12.698%	$96.7738	$96.77	$96.75	$96.80
Purchase #3	$188.39	6.635%	$200.8897	$200.89	$200.90	$200.90
Purchase #4	$115.54	10.310%	$127.4522	$127.45	$127.45	$127.50
Purchase #5	$248.79	12.459%	$279.7867	$279.79	$279.80	$279.80
Purchase #6	$142.46	3.831%	$147.9176	$147.92	$147.90	$147.90
Purchase #7	$177.38	3.202%	$183.0597	$183.06	$183.05	$183.10
7 purchase totals =	$1,057.35		$1,140.8447	$1,140.85	$1,140.80	$1,141.00