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	$86.74	3.608%	$89.8696	$89.87	$89.85	$89.90
Purchase #2	$182.48	3.508%	$188.8814	$188.88	$188.90	$188.90
Purchase #3	$39.30	3.683%	$40.7474	$40.75	$40.75	$40.70
Purchase #4	$103.45	12.383%	$116.2602	$116.26	$116.25	$116.30
Purchase #5	$248.50	5.159%	$261.3201	$261.32	$261.30	$261.30
Purchase #6	$37.84	7.809%	$40.7949	$40.79	$40.80	$40.80
Purchase #7	$67.88	3.820%	$70.473	$70.47	$70.45	$70.50
7 purchase totals =	$766.19		$808.3466	$808.34	$808.30	$808.40