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	$203.90	9.287%	$222.8362	$222.84	$222.85	$222.80
Purchase #2	$173.74	8.811%	$189.0482	$189.05	$189.05	$189.00
Purchase #3	$131.76	3.538%	$136.4217	$136.42	$136.40	$136.40
Purchase #4	$152.56	3.603%	$158.0567	$158.06	$158.05	$158.10
Purchase #5	$105.64	3.528%	$109.367	$109.37	$109.35	$109.40
Purchase #6	$188.38	9.664%	$206.585	$206.59	$206.60	$206.60
Purchase #7	$81.48	12.686%	$91.8166	$91.82	$91.80	$91.80
7 purchase totals =	$1,037.46		$1,114.1314	$1,114.15	$1,114.10	$1,114.10