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	$73.50	12.429%	$82.6353	$82.64	$82.65	$82.60
Purchase #2	$98.77	6.777%	$105.4636	$105.46	$105.45	$105.50
Purchase #3	$10.59	9.418%	$11.5874	$11.59	$11.60	$11.60
Purchase #4	$106.70	12.810%	$120.3683	$120.37	$120.35	$120.40
Purchase #5	$70.68	12.651%	$79.6217	$79.62	$79.60	$79.60
Purchase #6	$92.37	11.808%	$103.277	$103.28	$103.30	$103.30
Purchase #7	$135.72	7.121%	$145.3846	$145.38	$145.40	$145.40
7 purchase totals =	$588.33		$648.3379	$648.34	$648.35	$648.40