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	$168.83	10.650%	$186.8104	$186.81	$186.80	$186.80
Purchase #2	$250.31	7.630%	$269.4087	$269.41	$269.40	$269.40
Purchase #3	$57.59	3.752%	$59.7508	$59.75	$59.75	$59.80
Purchase #4	$42.82	3.792%	$44.4437	$44.44	$44.45	$44.40
Purchase #5	$223.72	9.575%	$245.1412	$245.14	$245.15	$245.10
Purchase #6	$244.83	10.867%	$271.4357	$271.44	$271.45	$271.40
Purchase #7	$20.87	10.781%	$23.12	$23.12	$23.10	$23.10
7 purchase totals =	$1,008.97		$1,100.1105	$1,100.11	$1,100.10	$1,100.00