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	$165.33	9.529%	$181.0843	$181.08	$181.10	$181.10
Purchase #2	$236.62	11.604%	$264.0774	$264.08	$264.10	$264.10
Purchase #3	$37.44	13.757%	$42.5906	$42.59	$42.60	$42.60
Purchase #4	$247.45	13.468%	$280.7766	$280.78	$280.80	$280.80
Purchase #5	$189.66	4.453%	$198.1056	$198.11	$198.10	$198.10
Purchase #6	$105.95	3.444%	$109.5989	$109.60	$109.60	$109.60
Purchase #7	$184.69	5.533%	$194.9089	$194.91	$194.90	$194.90
7 purchase totals =	$1,167.14		$1,271.1423	$1,271.15	$1,271.20	$1,271.20