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	$104.54	4.680%	$109.4325	$109.43	$109.45	$109.40
Purchase #2	$135.63	12.400%	$152.4481	$152.45	$152.45	$152.40
Purchase #3	$64.29	10.437%	$70.9999	$71.00	$71.00	$71.00
Purchase #4	$13.74	5.288%	$14.4666	$14.47	$14.45	$14.50
Purchase #5	$172.71	3.127%	$178.1106	$178.11	$178.10	$178.10
Purchase #6	$52.79	9.279%	$57.6884	$57.69	$57.70	$57.70
Purchase #7	$104.69	10.360%	$115.5359	$115.54	$115.55	$115.50
7 purchase totals =	$648.39		$698.6820	$698.69	$698.70	$698.60