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	$185.95	7.732%	$200.3277	$200.33	$200.35	$200.30
Purchase #2	$98.82	13.409%	$112.0708	$112.07	$112.05	$112.10
Purchase #3	$112.61	13.742%	$128.0849	$128.08	$128.10	$128.10
Purchase #4	$178.70	5.678%	$188.8466	$188.85	$188.85	$188.80
Purchase #5	$38.86	11.380%	$43.2823	$43.28	$43.30	$43.30
Purchase #6	$104.48	8.662%	$113.5301	$113.53	$113.55	$113.50
Purchase #7	$19.76	13.349%	$22.3978	$22.40	$22.40	$22.40
7 purchase totals =	$739.18		$808.5402	$808.54	$808.60	$808.50