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	$13.69	5.595%	$14.456	$14.46	$14.45	$14.50
Purchase #2	$109.50	12.424%	$123.1043	$123.10	$123.10	$123.10
Purchase #3	$213.90	3.666%	$221.7416	$221.74	$221.75	$221.70
Purchase #4	$203.29	8.478%	$220.5249	$220.52	$220.50	$220.50
Purchase #5	$140.88	9.251%	$153.9128	$153.91	$153.90	$153.90
Purchase #6	$199.86	6.674%	$213.1987	$213.20	$213.20	$213.20
Purchase #7	$89.97	11.717%	$100.5118	$100.51	$100.50	$100.50
7 purchase totals =	$971.09		$1,047.4501	$1,047.44	$1,047.40	$1,047.40